Endothelin antagonistic substance

ABSTRACT

Peptides having the formula: ##STR1## inhibit the binding of endothelin to its ET B  receptor and are useful in treating diseases associated with excess production or secretion of endothelin.

This application is continuation in part of patent application Ser. No. 07/884,642 filed on May 18, 1992, now abandoned, which is a divisional application of prior application Ser. No. 07/712,095 filed on Jun. 7, 1991, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novel compounds having antagonism against three endothelin isopeptides (endothelin-1, endothelin-2 and endothelin-3), which are physiologically highly active endogenous peptides, processes for their preparation and their use as a drug.

2. Discussion of Background

Two endothelin receptor subtypes ET_(A) and ET_(B) are known so far. The compounds of the present invention possess high affinity to at least the ET_(B) receptors, thereby inhibiting vasoconstriction and bronchoconstriction induced by the endothelins. The compounds of the present invention provide a new therapeutic potential, particularly for the treatment of hypertension, pulmonary hypertension, Raynaud's disease, acute renal failure, myocardial infarction, angina pectoris, cerebral infarction, cerebral vasospasm, arteriosclerosis, asthma, gastric ulcer, diabetes, endotoxin shock, endotoxin-induced multiple organ failure or disseminated intravascular coagulation, and/or cyclosporin-induced renal failure or hypertension.

Endothelin is a polypeptide composed of 21 amino acids, and it is produced by vascular endothelial cells of human or pig. Endothelin has a potent vasoconstrictor effect and a sustained and potent pressor action (Nature, 332, 411-415 (1988)).

Three endothelin isopeptides (endothelin-1, endothelin-2 and endothelin-3), which resemble one another in structure, exist in the bodies of animals including human, and these peptides have vasoconstriction and pressor effects (Proc. Natl. Acad, Sci, USA, 86, 2863-2867 (1989)).

As reported, the endothelin levels are clearly elevated in the blood of patients with essential hypertension, acute myocardial infarction, pulmonary hypertension, Raynaud's disease, diabetes or atherosclerosis, or in the washing fluids of the respiratory tract or the blood of patients with asthmaticus as compared with normal levels (Japan, J. Hypertension, 12, 79, (1989), J. Vascular Medicine Biology, 2, 207 (1990), Diabetologia, 33, 306-310 (1990), J. Am. Med. Association, 264, 2868 (1990), and The Lancet, ii, 747-748 (1989) and ii, 1144-1147 (1990)).

Further, an increased sensitivity of the cerebral blood vessel to endothelin in an experimental model of cerebral vasospasm (Japan. Soc. Cereb. Blood Flow & Metabol., 1, 73 (1989)), an improved renal function by the endothelin antibody in an acute renal failure model (J. Clin, Invest., 83, 1762-1767 (1989), and inhibition of gastric ulcer development with an endothelin antibody in a gastric ulcer model (Extract of Japanese Society of Experimental Gastric Ulcer, 50 (1991)) have been reported. Therefore, endothelin is assumed to be one of mediators causing acute renal failure or cerebral vasospasm following subarachnoid hemorrhage.

Further, endothelin is secreted not only by endothelial cells but also by tracheal epithelial cells or from kidney cells (FEBS Letters, 255, 129-132 (1989), and FEBS Letters, 249, 42-46 (1989)).

Endothelin was also found to control the release of physiologically active endogenous substances such as renin, atrial natriuretic peptide, endothelium-derived relaxing factor (EDRF), thromboxane A₂, prostacyclin, noradrenaline, angiotensin II and substance P (Biochem. Biophys, Res. Commun., 157, 1164-1168 (1988); Biochem. Biophys, Res. Commun., 155, 167-172 (1989); Proc. Natl. Acad. Sci. USA, 85, 9797-9800 (1989); J. Cardiovasc. Pharmacol., 13, S89-S92 (1989); Japan. J. Hypertension, 12, 76 (1989) and Neuroscience Letters, 102, 179-184 (1989)). Further, endothelin causes contraction of the smooth muscle of gastrointestinal tract and the uterine smooth muscle (FEBS Letters, 247, 337-340 (1989); Eur. J. Pharmacol., 154, 227-228 (1988); and Biochem. Biophys. Res. Commun., 159, 317-323 (1989)). Further, endothelin was found to promote proliferation of rat vascular smooth muscle cells, suggesting a possible relevance to the arterial hypertrophy (Atherosclerosis, 78, 225-228 (1989)). Furthermore, since the endothelin receptors are present in a high density not only in the peripheral tissues but also in the central nervous system, and the cerebral administration of endothelin induces a behavioral change in animals, endothelin is likely to play an important role for controlling nervous functions (Neuroscience Letters, 97, 276-279 (1989)). Particularly, endothelin is suggested to be one of mediators for pain (Life Sciences, 49, PL61-PL65 (1991)).

On the other hand, endotoxin is one of potential candidates to promote the release of endothelin. Remarkable elevation of the endothelin levels in the blood or in the culture supernatant of endothelial cells was observed when endotoxin was exogenously administered to animals or added to the culture endothelial cells, respectively. These findings suggest that endothelin is one of important mediators for endotoxin-induced diseases (Biochem. Biophys. Res. Commun., 161, 1220-1227 (1989); and Acta Physiol. Scand., 137, 317-318 (1989)).

Further, it was reported that cyclosporin remarkably increased endothelin secretion in the renal cell culture (LLC-PK1 cells) (Eur. J. Pharmacol., 180, 191-192 (1990)). Further, dosing of cyclosporin to rats reduced the glomerular filtration rate and increased the blood pressure in association with a remarkable increase in the circulating endothelin level. This cyclosporin-induced renal failure can be suppressed by the administration of endothelin antibody (Kidney Int., 37, 1487-1491 (1990)). Thus, it is assumed that endothelin is significantly involved in the pathogenesis of the cyclosporin-induced diseases.

Such various effects of endothelin are caused by the binding of endothelin to endothelin receptors widely distributed in many tissues (Am. J. Physiol., 256, R856-R866 (1989)).

It is known that vasoconstriction by the endothelins is caused via at least two subtypes of endothelin receptors (J. Cardiovasc. Pharmacol., 17(Suppl.7), S119-S121 (1991)). One of endothelin receptors is ET_(A) receptor selective to ET-1 rather than ET-3, and the other is ET_(B) receptor equally active to ET-1 and ET-3. These receptor proteins are reported to be different from each other (Nature, 348, 730-735 (1990)).

These two subtypes of endothelin receptors are differently distributed in tissues. It is known that the ET_(A) receptor is present mainly in cardiovascular tissues, whereas the ET_(B) receptor is widely distributed in various tissues such as brain, kidney, lung, heart and vascular tissues.

Substances which specifically inhibit the binding of endothelin to the endothelin receptors are believed to antagonize various pharmacological activities of endothelin and to be useful as a drug in a wide field. The present inventors already disclosed potent endothelin ET_(A) receptor antagonists in EP 0460679A2. Since, the action of the endothelins is caused via not only the ET_(A) receptor but also the ET_(B) receptor, novel substances with ET_(B) receptor antagonistic activity are desired to block activities of the endothelins in various diseases.

Endothelin is an endogenous substance which directly or indirectly (by controlling liberation of various endogenous substances) induces sustained contraction of vascular or non-vascular smooth muscles, and its excess production or excess secretion is believed to be one of pathogeneses for hypertension, pulmonary hypertension, Raynaud's disease, bronchial asthma, gastric ulcer, diabetes, arteriosclerosis, acute renal failure, myocardial infarction, angina pectoris, cerebral vasospasm and cerebral infarction. Further, it is suggested that endothelin serves as an important mediator involved in disease such as endotoxin shock, endotoxin-induced multiple organ failure or disseminated intravascular coagulation, and/or cyclosporin-induced renal failure or hypertension. Two endothelin receptors ET_(A) and ET_(B) are known so far. An antagonistic agent against the ET_(B) receptor as well as the ET_(A) receptor is useful as a drug. Accordingly, it is an object of the present invention to provide a novel therapeutics for the treatment of the above-mentioned various diseases by an invention of a potent ET_(B) receptor antagonist.

In order to accomplish the above object, the present inventors have synthesized various peptide derivatives and have investigated their endothelin antagonistic activities, and as a result have found that novel peptide derivatives represented by the following formula (I) and their pharmaceutically acceptable salts have strong potent ET_(B) receptor antagonistic activities. The present invention has been accomplished on the basis of this discovery.

Thus, the present invention provides a peptide derivative of the formula: ##STR2## wherein A is a group of the formula R¹¹ O--CO-- (wherein R¹¹ is a lower alkyl group or a phenyl group), or a group of the formula R¹² R¹³ N--C(═O)-- (wherein R¹² is a lower alkyl group, a cycloalkyl group, a 1-adamantyl group, a phenyl group wherein one or two optional hydrogen atoms on the benzene ring may independently be replaced by a halogen atom, a trifluoromethyl group, a nitro group, an amino group or a formylamino group, a pyridyl group, or a thienyl group, R¹³ is a hydrogen atom, a lower alkyl group or a cycloalkyl group, or R¹² and R¹³ form, together with the adjacent nitrogen atom, a 5- to 9-membered nitrogen-containing saturated heterocyclic ring having 4 to 8 carbon atoms, wherein among methylene groups forming the ring, one optional methylene group not adjacent to the above nitrogen atom may be replaced by a thio group, and one to four optional hydrogen atoms on the carbon atoms of the heterocyclic ring may independently be replaced by a lower alkyl group, and further two adjacent carbon atoms in the heterocyclic ring may form a benzo-fused ring); B is an oxygen atom or a group of the formula --NR² -- (wherein R² is a hydrogen atom or a lower alkyl group); R³ is a lower alkyl group, a cycloalkyl group, an aryl group, a heterocyclic group, a cycloalkyl lower alkyl group, an aryl lower alkyl group or a heterocyclic lower alkyl group; X¹ is an oxygen atom or a group of the formula --NR⁴ -- (wherein R⁴ is a hydrogen atom or a lower alkyl group); R⁵ is a 3-indolylmethyl, 3-benzothienylmethyl, 1-naphthylmethyl or benzyl group wherein one or two optional hydrogen atoms on the ring may be replaced by a hydroxyl group, a formyl group, a lower alkyl group, a lower alkoxy group, a lower alkoxycarbonyl group, a nitro group or a group of the formula R⁵¹ --CO--X² {wherein R⁵¹ is a lower alkyl group, a lower alkoxy group, or an amino group which may be substituted by a lower alkyl group, and X² is an oxygen atom or a group of the formula --NR⁵² -- (wherein R⁵² is a hydrogen atom or a lower alkyl group)}; X³ is an oxygen atom or a sulfur atom; R⁶ is a hydrogen atom, or a lower alkyl or lower alkenyl group which may have a substituent selected from the group consisting of a hydroxyl group, a lower alkoxy group, a lower alkylthio group and a heterocyclic group; n is 0 or 1; Y is a hydroxymethyl group, a group of the formula CO₂ R⁷¹ (wherein R⁷¹ is a hydrogen atom or a lower alkyl group), a group of the formula CONHR⁷² (wherein R⁷² is a hydrogen atom or a lower alkyl group which may have a substituent selected from the group consisting of a hydroxyl group, a carboxyl group and a sulfo group), a 1H-tetrazol-5-yl group, a sulfo group and a phosphono group; or a pharmaceutically acceptable salt thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the activities of 10 μM of Compound 4 (∘) against endothelin-3-induced contraction of isolated guinea pig bronchial tube as compared with the case in which no drug is present ().

FIG. 2 shows the activities of 10 μM of Compound 39 (∘) against endothelin-3-induced contraction of isolated guinea pig bronchial tube as compared with the case in which no drug is present ().

FIG. 3 shows the activities of 10 μM of Compound 40 (∘) against endothelin-3-induced contraction of isolated guinea pig bronchial tube as compared with the case in which no drug is present ().

Now, the present invention will be described in further detail with reference to the preferred embodiments.

Now, the meanings of various abbreviations used in this specification will be given.

    ______________________________________                                         Abbreviation Meaning of Abbreviation                                           ______________________________________                                         DβAbu   D-3-aminobutyric acid                                             DBal         D-3-(3-benzothienyl)alanine                                       Ile          L-isoleucine                                                      DIle         D-isoleucine                                                      Leu          L-leucine                                                         γMeLeu γ-methyl-L-leucine                                          DMet         D-methionine                                                      DNal         D-3-(l-naphthyl)alanine                                           Nle          L-norleucine                                                      DNle         D-norleucine                                                      Nva          L-norvaline                                                       DNva         D-norvaline                                                       DPhe(m-NO.sub.2)                                                                            D-3-(3-nitrophenyl)alanine                                        DPhe(m-NH.sub.2)                                                                            D-3-(3-aminophenyl)alanine                                        DLPhe(3-COOEt)                                                                              DL-3-(3-ethoxycarbonylphenyl)alanine                              DLPhe(3-COOMe)                                                                              DL-3-(3-                                                                       methoxycarbonylphenyl)alanine                                     DSer         D-serine                                                          DSer(Me)     O-methyl-D-serine                                                 D-mTyr       D-methatyrosine                                                   DL-mTyr      DL-methatyrosine                                                  DTrp         D-tryptophan                                                      DTrp(7-OBzl) D-(7-benzyloxy)tryptophan                                         DTrp(7-OH)   D-(7-hydroxy)tryptophan                                           DTrp(COOEt)  D-(N.sup.in -ethoxycarbonyl)tryptophan                            DTrp(COOMe)  D-(N.sup.in -methoxycarbonyl)tryptophan                           DTrp(OH)     D-(N.sup.in -hydroxy)tryptophan                                   DTrp(OMe)    D-(N.sup.in -methoxy)tryptophan                                   DLTrp(Me)    DL-(N.sup.in -methyl)tryptophan                                   Ac           acetyl                                                            Boc          tert-butoxycarbonyl                                               Et           ethyl                                                             Me           methyl                                                            .sup.n Pr    n-propyl                                                          .sup.i Pr    isopropyl                                                         .sup.n Bu    n-butyl                                                           .sup.t Bu    tert-butyl                                                        Ph           phenyl                                                            Bzl          benzyl                                                            c-Pent       cyclopentyl                                                       Cpeg         L-cyclopentylglycine                                              Cprg         L-cyclopropylglycine                                              CDI          1,1'-carbonyldiimidazole                                          DCC          N,N'-dicyclohexylcarbodiimide                                     DMAP         4-(dimethylamino)pyridine                                         DMF          N,N-dimethylformamide                                             DMSO         dimethylsulfoxide                                                 NMP          N-methylpyrrolidone                                               NMM          N-methylmorpholine                                                EDCI.HCl     1-ethyl-3-(3-dimethylaminopropyl)-                                             carbodiimide.hydrochloride                                        HOBT.H.sub.2 O                                                                              1-hydroxy-lH-benzotriazole.                                                    monohydrate                                                       HOSu         N-hydroxysuccinimide                                              TBAHS        tetra-n-butylammonium                                                          hydrogensulfate                                                   TEA          triethylamine                                                     TFA          trifluoro acetic acid                                             THF          tetrahydrofuran                                                   TsOH         p-toluene sulfonic acid                                           Ts           p-toluenesulfonyl                                                 Z            benzyloxycarbonyl                                                 MOPS         3-morpholinopropane sulfonic acid                                 HEPES        2-[4-(2-hydroxyethyl)-l-                                                       piperazinyl]-ethane sulfonic acid                                 Tris         tris(hydroxymethyl)aminomethane                                   PMSF         phenylmethanesulfonyl═fluoride                                ______________________________________                                    

Now, the definitions of the various terms mentioned in this specification will be explained.

In this specification, the lower alkyl group means a linear or branched alkyl group having 1 to 6 carbon atoms such as a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, 1-methylbutyl, 2-methylbutyl, 1,2-dimethylpropyl, 1-ethylpropyl, hexyl, isohexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 2,2-dimethylbutyl, 1-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-2-methylpropyl or 1-ethyl-1-methylpropyl group.

The cycloalkyl group may, for example, be a cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl or cyclononyl group.

The aryl group may, for example, be a phenyl, 1-naphthyl or 2-naphthyl group.

The heterocyclic group means a heterocyclic or fused heterocyclic group containing at least one hetero atom such as an oxygen, nitrogen or sulfur atom, for example, a thienyl, furyl, thiazolyl, imidazolyl, pyridyl, indolyl or benzothienyl group.

The lower alkenyl group means a linear or branched alkenyl group having 1 to 6 carbon atoms such as a vinyl, allyl, 2-propenyl, isopropenyl, 3-butenyl, 2-butenyl, 1-butenyl, 1-methyl-2-propenyl, 1-methyl-1-propenyl, 1-ethyl-1-ethenyl, 2-methyl-2-propenyl, 2-methyl-1-propenyl, 4-pentenyl or 5-pentenyl group.

The lower alkoxy group means a linear or branched alkoxy group having 1 to 6 carbon atoms such as a methoxy, ethoxy, propoxy or isopropoxy group.

The lower alkanoyloxy group means a linear or branched alkanoyloxy group having 2 to 6 carbon atoms such as an acetoxy or propionyloxy group.

The halogen atom means a fluorine, chlorine, bromine or iodine atom.

Now, this invention will be described in more detail with reference to specific examples for the various symbols used in the formula (I).

In A, R¹¹ means a lower alkyl group or a phenyl group. Examples of the lower alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, 1,1-dimethylbutyl, 1-ethyl-1-methylpropyl and 1,1,2-trimethylpropyl groups.

In A, R¹² means a lower alkyl group, a cycloalkyl group, a 1-adamantyl group, a phenyl group wherein 1 or 2 optional hydrogen atoms on the benzene ring may be replaced by an optional group selected from the group consisting of a halogen atom, a trifluoromethyl group, a nitro group, an amino group and a formylamino group, a pyridyl group or a thienyl group. Otherwise, R¹² and R¹³ may form, together with the adjacent nitrogen atom, a heterocyclic group as indicated below. Examples of the lower alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, 1,1-dimethylbutyl, 1-ethyl-1-methylpropyl and 1,1,2-trimethylpropyl groups. Examples of the cycloalkyl group are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl groups. Examples of the phenyl group wherein 1 or 2 optional hydrogen atoms on the benzene ring may be replaced by an optional group selected from the group consisting of a halogen atom, a trifluoromethyl group, a nitro group, an amino group and a formylamino group, are phenyl, 2-fluorophenyl, 2-chlorophenyl, 2-bromophenyl, 3-fluorophenyl, 3-chlorophenyl, 3-bromophenyl, 4-fluorophenyl, 4-chlorophenyl, 4-bromophenyl, 2,6-difluorophenyl, 2,6-dichlorophenyl, 2,6-dibromophenyl, 2-aminophenyl, 2-formylaminophenyl, 2-trifluoromethylphenyl, 2-nitrophenyl, 3-aminophenyl and 3-formylaminophenyl groups. Examples of the pyridyl group are 2-pyridyl, 3-pyridyl and 4-pyridyl groups. Examples of the thienyl group are 2-thienyl and 3-thienyl groups.

In A, R¹³ means a hydrogen atom, a lower alkyl group or a cycloalkyl group. Otherwise, R¹³ and R¹² may form, together with the adjacent nitrogen atom, a heterocyclic group as indicated below. Examples of the lower alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl and tert-pentyl groups. Examples of the cycloalkyl group are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl groups.

In A, R¹² and R¹³ may also form, together with the adjacent nitrogen atom, a 5- to 9-membered nitrogen-containing saturated heterocyclic group having 4 to 8 carbon atoms. Among methylene groups forming the heterocycle, one optional methylene group not adjacent to the above nitrogen atom may be replaced by a thio group, and one to four optional hydrogen atoms on the carbon atoms of the heterocycle may independently be replaced by a lower alkyl group, and further two adjacent carbon atoms in the heterocycle may form a fused-benzene ring. Examples of the heterocyclic group are pyrrolidino, piperidino, perhydroazepin-1-yl, perhydroazocin-1-yl, perhydroazonin-1-yl, 1,3-thiazolidin-1-yl, indolin-1-yl, isoindolin-2-yl, 3-pyrolin-1-yl, 1,5-dihydro-2H-pyrrol-1-yl, perhydro-1,4-thiadin-4-yl, 1,2,3,4-tetrahydroquinolin-1-yl, 1,2,3,4-tetrahydroisoquinolin-2-yl, 1,2,3,4-tetrahydropyridin-1-yl, 1,2,3,6-tetrahydropyridin-1-yl, perhydro-1,4-thiazepin-4-yl, 2,3,4,5-tetrahydro-1-benzazepin-1-yl, 2,3,4,5-tetrahydro-2-benzazepin-2-yl, 1,2,4,5-tetrahydro-3-benzazepin-3-yl, 2,3,4,5-tetrahydro-1H-azepin-1-yl, 2,3,6,7-tetrahydro-1H-azepin-1-yl, 1,3,4,7-tetrahydro-2H-azepin-1-yl, perhydro-1,4-thiazocin-4-yl, 1,2,3,4,5,6-hexahydro-1-benzazocin-1-yl, 1,2,3,4,5,6-hexahydro-2-benzazocin-2-yl, 1,2,3,4,5,6-hexahydro-3-benzazocin-3-yl, 1,2,3,4,5,6-hexahydroazocin-1-yl, 1,2,3,4,7,8-hexahydroazocin-1-yl and 1,2,3,4,5,8-hexahydroazocin-1-yl groups, or the above-mentioned heterocyclic groups wherein one to four optional hydrogen atoms on the carbon atoms of the heterocycle may independently be replaced by a lower alkyl group. Examples of the lower alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl groups.

In B, R² means a hydrogen atom or a lower alkyl group. Examples of the lower alkyl group are methyl and ethyl groups.

R³ means a lower alkyl group, a cycloalkyl group, an aryl group, a heterocyclic group, a cycloalkyl lower alkyl group, an aryl lower alkyl group or a heterocyclic lower alkyl group. Examples of the lower alkyl group are propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl and tert-pentyl groups. Examples of the cycloalkyl group are cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl groups. An example of the aryl group is a phenyl group. Examples of the heterocyclic group are 2-thienyl, 3-thienyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, 2-furyl and 3-furyl groups. Examples of the cycloalkyl lower alkyl group are cyclopropylmethyl, 1-cyclopropylethyl, 2-cyclopropylethyl, 1-cyclopropyl-1-methylethyl, cyclobutylmethyl, 1-cyclobutylethyl, 2-cyclobutylethyl, 1-cyclobutyl-1-methylethyl, cyclopentylmethyl, 1-cyclopentylethyl, 2-cyclopentylethyl, 1-cyclopentyl-1-methylethyl, 1-cyclohexylmethyl, 1-cyclohexylethyl, 1-cyclohexyl-1-methylethyl, 1-cycloheptylmethyl, 1-cycloheptylethyl, 1-cyclooctylmethyl and 1-cyclooctylethyl groups. Examples of the aryl lower alkyl group are benzyl and phenylethyl groups. Examples of the heterocyclic lower alkyl group are 2-thienylmethyl, 3-thienylmethyl, 2-thienylethyl, 2-thiazolylmethyl, 2-furylmethyl, 3-furylmethyl, 2-pyridylmethyl, 3-pyridylmethyl, 4-pyridylmethyl, 2-indolylmethyl, 3-indolylmethyl, 2-benzothienylmethyl and 3-benzothienylmethyl groups.

In X¹, R⁴ means a hydrogen atom or a lower alkyl group. Examples of the lower alkyl group are methyl and ethyl groups.

R⁵ is a 3-indolylmethyl, 3-benzothienylmethyl, 1-naphthylmethyl group or benzyl group wherein one or two optional hydrogen atoms on the ring may be replaced by a hydroxyl group, a formyl group, a lower alkyl group, a lower alkoxy group, a lower alkoxycarbonyl group, a nitro group or a group of the formula R⁵¹ --CO--X² -- {wherein R⁵¹ is a lower alkyl group, a lower alkoxy group, or an amino group which may be replaced by a lower alkyl group, and X² is an oxygen atom or a group of the formula --NR⁵² -- (wherein R⁵² is a hydrogen atom or a lower alkyl group)}. Examples of the substituted or unsubstituted 3-indolylmethyl, 3-benzothienylmethyl, 1-naphthylmethyl or benzyl group, are 3-indolylmethyl, (1-methoxycarbonyl-3-indolyl)methyl, (1-ethoxycarbonyl-3-indolyl)methyl, (1-propoxycarbonyl-3-indolyl)methyl, (1-isopropoxycarbonyl-3-indolyl)methyl, (1-butoxycarbonyl-3-indolyl)methyl, (1-isobutoxycarbonyl-3-indolyl)methyl, (1-sec-butoxycarbonyl-3-indolyl)methyl, (1-tert-butoxycarbonyl-3-indolyl)methyl, (1-formyl-3-indolyl)methyl, (1-hydroxyl-3-indolyl)methyl, (7-hydroxy-3-indolyl)methyl, (1-methyl-3-indolyl)methyl, (1-methoxy-3-indolyl)methyl, (7-methoxy-3-indolyl)methyl, (1-acetoxy-3-indolyl)methyl, (2-acetoxy-3-indolyl)methyl, (7-acetoxy-3-indolyl)methyl, (7-hydroxy-1-methoxycarbonyl-3-indolyl)methyl, (7-methoxy-1-methoxycarbonyl-3-indolyl)methyl, 2-nitrophenylmethyl, 3-nitrophenylmethyl, 4-nitrophenylmethyl, 2-methoxycarbonylphenylmethyl, 3-methoxycarbonylphenylmethyl, 4-methoxycarbonylphenylmethyl, 2-ethoxycarbonylphenylmethyl, 3-ethoxycarbonylphenylmethyl, 4-ethoxycarbonylphenylmethyl, 2-acetoxyphenylmethyl, 3-acetoxyphenylmethyl, 4-acetoxyphenylmethyl, 2-methoxycarbonyloxyphenylmethyl, 3-methoxycarbonyloxyphenylmethyl, 4-methoxycarbonyloxyphenylmethyl, 2-carbamoyloxyphenylmethyl, 3-carbamoyloxyphenylmethyl, 4-carbamoyloxyphenylmethyl, 2-methylcarbamoyloxyphenylmethyl, 3-methylcarbamoyloxyphenylmethyl, 4-methylcarbamoyloxyphenylmethyl, 2-dimethylcarbamoyloxyphenylmethyl, 3-dimethylcarbamoyloxyphenylmethyl, 4-dimethylcarbamoyloxyphenylmethyl, 2-acetamidophenylmethyl, 3-acetamidophenylmethyl, 4-acetamidophenylmethyl, 2-methoxycarbonylaminophenylmethyl, 3-methoxycarbonylaminophenylmethyl, 4-methoxycarbonylaminophenylmethyl, 2-ureidophenylmethyl, 3-ureidophenylmethyl, 4-ureidophenylmethyl, 2-(3-methylureido)phenylmethyl, 3-(3-methylureido)phenylmethyl, 4-(3-methylureido)phenylmethyl, 2-(3,3-dimethylureido)phenylmethyl, 3-(3,3-dimethylureido)phenylmethyl, 4-(3,3-dimethylureido)phenylmethyl, 2-hydroxyphenylmethyl, 3-hydroxyphenylmethy, 4-hydroxyphenylmethyl, 2-methoxyphenylmethyl, 3-methoxyphenylmethyl and 4-methoxyphenylmethyl groups.

Among them, preferred are 3-indolylmethyl groups wherein the 1- or 2-position of the indole ring may be substituted by 1 to 2 substituents selected from the group consisting of a lower alkoxy group, a lower alkanoyloxy group and a lower alkoxycarbonyl group, such as, 3-indolylmethyl, (1-methoxycarbonyl-3-indolyl)methyl, (1-ethoxycarbonyl-3-indolyl)methyl, (1-propoxycarbonyl-3-indolyl)methyl, (1-isopropoxycarbonyl-3-indolyl)methyl, (1-butoxycarbonyl-3-indolyl)methyl, (1-isobutoxycarbonyl-3-indolyl)methyl, (1-sec-butoxycarbonyl-3-indolyl)methyl, 1-tert-butoxycarbonyl-3-indolyl)methyl, (1-acetoxy-3-indolyl)methyl, (2-acetoxy-3-indolyl)methyl, (7-acetoxy-3-indolyl)methyl, (1-methoxy-3-indolyl)methyl, (7-methoxy-3-indoyl)methyl and (7-methoxy-1-methoxycarbonyl-3-indolyl)methyl groups.

R⁶ means a hydrogen atom, or a lower alkyl or lower alkenyl group which may have 1 to 3 substituents selected from the group consisting of hydroxyl, lower alkoxy, lower alkylthio and heterocyclic groups. Examples of the lower alkyl or lower alkenyl group which may be substituted by 1 to 3 substituents selected from the group consisting of hydroxyl, lower alkoxy, lower alkylthio and heterocyclic groups, are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, hydroxymethyl, 1-hydroxyethyl, methoxymethyl, 1-methoxyethyl, methylthiomethyl, ethylthiomethyl, propylthiomethyl, butylthiomethyl, 2-methylthioethyl, 2-ethylthioethyl, 3-indolylmethyl, 4-imidazolylmethyl, vinyl, allyl, 2-propenyl, isopropenyl, 3-butenyl, 2-butenyl, 1-butenyl, 1-methyl-2-propenyl, 1-methyl-1-propenyl, 1-ethyl-1-ethenyl, 2-methyl-2-propenyl, 2-methyl-1-propenyl, 4-pentenyl, 5-pentenyl, 1-hydroxy-2-propenyl, 1-methoxy-2-propenyl, 1-methylthio-2-propenyl, 2-hydroxy-3-butenyl and 2-ethylthio-3-butenyl groups. Among them, preferred are a lower alkyl or lower alkenyl group which may have a substituent selected from the group consisting of lower alkoxy and lower alkylthio groups, such as, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, neopentyl, tert-pentyl, hexyl, methoxymethyl, 1-methoxyethyl, methylthiomethyl, ethylthiomethyl, propylthiomethyl, butylthiomethyl, 2-methylthioethyl, 2-ethylthioethyl, vinyl, allyl, 2-propenyl, isopropenyl, 3-butenyl, 2-butenyl, 1-butenyl, 1-methyl-2-propenyl, 1-methyl-1-propenyl, 1-ethyl-1-ethenyl, 2-methyl-2-propenyl, 2-methyl-1-propenyl, 4-pentenyl, 1-hydroxy-2-propenyl, 1-methoxy-2-propenyl, 1-methylthio-2-propenyl, 2-hydroxy-3-butenyl and 2-ethylthio-3-butenyl groups.

R⁷¹ means a hydrogen atom or a lower alkyl group. Examples of the lower alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl and hexyl groups.

R⁷² means a hydrogen atom or a lower alkyl group which may be substituted by a substituent selected from the group consisting of hydroxyl, carboxyl, and sulfo groups. Examples of the lower alkyl group which may be substituted by a substituent selected from the group consisting of hydroxyl, carboxyl, and sulfo groups, are 2-hydroxyethyl, carboxymethyl, 1-carboxyethyl, 2-carboxyethyl, sulfomethyl and 2-sulfoethyl groups.

Now, the process for producing the novel peptide derivatives of the present invention will be described.

A peptide derivative of the present invention can be prepared by a method wherein amino acids composing the target peptide derivative are condensed one by one, and then, if necessary, removing a C-terminal protective group (Method 1). Peptide derivatives prepared by Method 1 can be converted into other peptide derivatives of the present invention, as the case requires, by a combination of the following reactions: (1) alkoxycarbonylation, aryloxycarbonylation or carbamoylation of the N-terminal α-amino group after removal of an N-terminal amino-protecting group (Methods 2 and 3), and (2) alkoxycarboylation (Method 4) or hydroxylation or alkoxylation (Method 5) at the 1-position of the indole ring of tryptophan. Furthermore, these peptide derivatives can, if necessary, be converted to pharmaceutically acceptable salts.

Each method will be detailed as follows.

[Method 1]

Method 1 is a conventional synthetic method for peptides, that is, a method wherein amino acids or amino acid derivatives are condensed one by one to prepare a desired peptide derivative. Furthermore, after condensation, a C-terminal protective group can be removed by alkaline hydrolysis, catalytic hydrogenation or acid decomposition. Condensation can be conducted according to known methods such as a DCC method, an azide method, an active ester method and a mixed acid anhydride method (described, for example, by M. Bodansky and M. A. Ondetti in Peptide Synthesis, Interscience, New York, 1966; by F. M. Finn and K. Holmann in The Proteins, Vol. 2, ed. by H. Nenrath and R. L. Hill, Academic Press Inc., New York, 1976; by Nobuo Izumiya et al. in Peptide Synthesis, Maruzen, 1975).

For example, in the case wherein condensation is carried out by a DCC method, an α-amino acid derivative or an α-hydroxycarboxylic acid derivative of the formula ##STR3## wherein T is A or an α-amino-protecting group, and A, B and R³ are as defined before, is treated with a condensing reagent such as DCC(or EDCI.HCl)-HOBT.H₂ O in a suitable solvent such as DMSO, NMP, DMF, THF, 1,4-dioxane, acetonitrile, dichloromethane or chloroform at around -40° C. to room temperature, then condensed with an α-amino acid derivative or an α-hydroxycarboxylic acid derivative having an α-carboxyl-protecting group, of the formula: ##STR4## wherein P¹ is an α-carboxyl-protecting group, and X¹ and R⁵ are as defined before, to afford a dipeptide derivative of the formula: ##STR5## wherein T, B, R³, R⁵, X¹ and P¹ are as defined before. An N-terminal α-amino-protecting group is usually selected from the groups well-known to those skilled in the art, for example, from urethane type protective groups such as a Z group, a Boc group, a p-methoxybenzyloxycarbonyl group and a p-nitrobenzyloxycarbonyl group, while the C-terminal α-carboxyl group is usually protected as, for example, a methyl ester, an ethyl ester, a benzyl ester or a tert-butyl ester. Each protective group should be selected so that it can be selectively deprotected after condensation. For example, in the case that a Boc group is selected as an N-terminal protective group, it is preferable to protect the C-terminus as a methyl group, an ethyl group or a benzyl group. A Boc group will be readily removed by use of a mild acid such as TFA, while the carboxyl-protecting groups described above will be usually intact under these conditions. On the other hand, a methyl, ethyl or benzyl ester will be easily deprotected by alkaline hydrolysis and a benzyl ester will be also deprotected by catalytic hydrogenation, while a Boc group will be intact under these conditions.

In the case that T is an α-amino-protecting group, the group T will be formally converted to A by removal of T from the dipeptide derivative (IV) followed by N-alkoxycarbonylation, N-aryloxycarbonylation or N-carbamoylation which will be carried out under the reaction conditions described later in Method 2.

A C-terminal protective group of the dipeptide derivative (IV) prepared in the above-mentioned manner is now removed, and the resulting deprotected dipeptide is treated with a condensation reagent (for example, EDCI.HCl-HOBT.H₂ O) in the same manner described above and then with an amino acid whose C-terminal carboxyl group is protected, to afford a desired peptide derivative.

In the case that each of B and X¹ is --NR² -- or --NR⁴ --, and P¹ is a lower alkyl group or a benzyl group, the dipeptide derivative (IV) may be treated with an excess amount of hydrazine in a solvent such as methanol or DMF at room temperature to afford the corresponding hydrazide, which can be converted to a desired peptide derivative by an azide method. Namely, the hydrazide is first converted to the corresponding azide on treatment with a reagent such as a lower alkyl ester of nitrous acid (for example, tert-butyl nitrite or isoamyl nitrite) or an alkaline metal salt of nitrous acid (for example, sodium nitrite or potassium nitrite) in the presence of a strong acid such as hydrochloric acid or sulfuric acid (this reaction can be performed in a solvent such as water, and/or DMF, THF or 1,4-dioxane at around -60° C. to -15° C.). Then, the azide is mixed with a tertiary amine such as TEA, and a C-terminal ester derivative of an amino acid at -70° C. to -60° C., and then allowed to react at -20° C. to room temperature to afford a desired peptide derivative. A tetrabutylammonium-, triethylammonium-, sodium- or potassium-salt of an amino acid can also be used instead of the C-terminal ester derivative.

In the process so far described, a C-terminal amino acid or a C-terminal dipeptide is lastly condensed to give a target peptide derivative. The alternative process wherein an N-terminal amino acid is lastly condensed to give a target product is also available. Namely, a compound of the formula: ##STR6## wherein P² is a hydrogen atom or an α-amino-protecting group, and R⁵ and X¹ are as defined before, is condensed with a compound of the formula: ##STR7## wherein n, R⁶ and Y are as defined before, by a DCC method or an azide method to afford an N-terminal protected peptide derivative or α-hydroxycarboxylic acid derivative. A suitable α-amino-protecting group can be selected from the urethane type protective groups described before, and a C-terminal carboxyl group can be protected as an ester. In the case that a C-terminal carboxyl group is protected as, for example, a tert-butyl ester, a Z group or a Boc group is preferable for a N-terminal amino-protecting group. A Z group will be readily removed by catalytic hydrogenation and a Boc group will be readily removed by treatment with a mild acid such as formic acid or TFA under ice-cooling, while under these conditions these C-terminal carboxyl-protecting groups will be intact.

An α-hydroxycarboxylic acid derivative or a dipeptide derivative (in the case of a dipeptide derivative, an N-terminal amino protecting group is removed prior to following treatments) prepared in the above-mentioned manner is treated with a condensation reagent (for example, EDCI.HCl-HOBT.H₂ O) in the same manner described above and then with an N.sup.α -substituted amino acid or an O.sup.α -substituted hydroxycarboxylic acid, to afford a desired peptide derivative. A peptide derivative of the formula (I) wherein X³ is a sulfur atom, can be prepared by condensation of a compound of the formula (V) with a compound of the formula (VI) whose C-terminal carboxyl group is protected, followed by conversion of the resulting amide bond to the thioamide bond on treatment with, for example, the Lawesson's reagent, then condensed with a compound of the formula (II) by, for example, a DCC method or an azide method to afford a target peptide derivative elongated toward the N-terminus.

A C-terminal protective group of a peptide derivative prepared by the method so far described, can be deprotected by a suitable method, if necessary. For example, in the case that a carboxyl group is protected as a tert-butyl ester, the protective group can be readily removed by acid decomposition, that is, by treatment with a mild acid such as formic acid or TFA. In the case that a carboxylic acid is protected as a benzyl ester, the protective group can be readily removed by catalytic hydrogenation, that is, by hydrogenation under 1 to 4 atmospheric pressures of hydrogen in the presence of a catalyst such as Pd--C or palladium black in a solvent such as methanol, ethanol, DMF, THF, 1,4-dioxane or acetic acid.

[Method 2]

Method 2 is a process for producing a peptide derivative which possesses an alkoxycarbonyl, aryloxycarbonyl or carbamoyl group at the N-terminus, wherein an N-terminal amino protective group of an amino acid derivative or a peptide derivative prepared by Method 1, is removed, and the resulting deprotected amino group is reacted with an acid chloride such as a chloroformate (R¹¹ OCOCl) or a carbamoyl chloride (R¹² R¹³ NCOCl) in the presence of a base, or reacted with an isocyanate (R¹² NCO) (wherein R¹¹, R¹² and R¹³ are as defined before), furthermore, a C-terminal protective group is optionally removed by alkaline hydrolysis, catalytic hydrogenation or acid decomposition.

An N-terminal protective group of the precursor can be readily removed by a conventional method such as catalytic hydrogenation (a Z group) or by treatment with a mild acid such as TFA (a Boc group). The reaction of the resulting deprotected peptide derivative from which the N-terminal amino protective group is removed by the method described above, with an acid chloride such as a chloroformate (R¹¹ OCOCl) or a carbamoyl chloride (R¹² R¹³ NCOCl) can be performed in a suitable solvent such as chloroform, dichloromethane, THF, 1,4-dioxane, toluene or pyridine in the presence of a base such as TEA, DMAP, N-methylmorpholine or pyridine at 0° C. to the boiling point of the solvent. The reaction with an isocyanate (R¹² NCO) can be performed in a solvent such as chloroform, dichloromethane, THF, 1,4-dioxane or toluene at 0° C. to the boiling point of the solvent.

A C-terminal protective group of peptide derivatives prepared by the above-mentioned method can be removed by alkaline hydrolysis, catalytic hydrogenation or acid decomposition in the same manner described in Method 1, if necessary.

[Method 3]

Method 3 is a process for producing an amino acid or a peptide derivative which possesses a carbamoyl group at the N-terminus, by treatment of an amino acid derivative or a peptide derivative (prepared by Method 1 or 2) having an aryloxycarbonyl group at the N-terminus, with a primary or secondary amine R¹² NHR¹³ wherein R¹² and R¹³ are as defined before, furthermore optionally removing a C-terminal protective group by alkaline hydrolysis, catalytic hydrogenation or acid decomposition.

That is, a peptide derivative possessing a carbamoyl group at the N-terminus can be prepared by dissolving a peptide derivative possessing an aryloxycarbonyl group at the N-terminus in a solvent such as chloroform, dichloromethane, THF, 1,4-dioxane, toluene or pyridine, followed by addition of the primary or secondary amine described above, optional addition of a tertiary amine such as TEA or DMAP, and allowing them to react at room temperature to the boiling point of the solvent. A C-terminal protective group of the product can be removed, if necessary, by alkaline hydrolysis, catalytic hydrogenation or acid decomposition in the same manner described in Method 1.

[Method 4]

Method 4 is a process for alkoxycarbonylation at the 1-position of the indole ring of a tryptophanyl residue when the peptide derivative prepared in the present invention contains the tryptophanyl residue.

The alkoxycarbonylation of the indole ring at the 1-position can be performed on treatment of a tryptophan-containing dipeptide or tripeptide derivative prepared by optionally combining Methods 1, 2 and 3, or an optionally protected tryptophan derivative as a starting material thereof, with a base (such as sodium hydroxide) and alkyl chloroformate in a solvent such as dichloromethane in the presence of TBAHS.

[Method 5]

Method 5 is a process for hydroxylation or lower alkoxylation at the 1-position of the indole ring when the peptide derivative prepared in the present invention contains a tryptophanyl residue.

The hydroxylation of the indole ring at the 1-position can be performed on treatment of a tryptophan-containing dipeptide or tripeptide derivative prepared by optionally combining Methods 1, 2, and 3, or an optionally protected tryptophan derivative as a starting material thereof, with sodium cyanoborohydride in a solvent such as acetic acid, and treatment of the resulting indoline derivative with hydrogen peroxide in methanol, water or a mixed solvent thereof. The lower alkoxylation of the indole ring at the 1-position can be performed by treatment of the hydroxylated derivative with, for example, diazomethane or diazoethane.

All reaction intermediates and products so far described can be purified by well-known methods such as recrystallization, reprecipitation, partition procedures, normal- or reverse-phase chromatography and ion-exchange chromatography.

Starting materials used in the methods so far described are commercially available except for the following materials, which are prepared by the known method in the literature.

DL-3-(3-ethoxycarbonylphenyl)alanine and DL-3-(4-methoxycarbonylphenyl)alanine: Synthesis, 53 (1984).

D-3-(3-benzothienyl)alanine: Chem. Pharm. Bull., 24, 3149 (1976).

D-S-methylcysteine, D-S-ethylcysteine, D-S-n-propylcysteine: by Nobuo Izumiya et al in Peptide Synthesis, Maruzen, 1975.

D-norleucinol: synthesized in the same manner described in J. Am. Chem. Soc., 107, 7974 (1985).

D-3-cyclopropylalanine: J. Am. Chem. Soc., 111, 6354 (1989).

D-cyclopropylglycine: J. Am. Chem. Soc., 111, 6354 (1989).

D-cyclopentylglycine: J. Org. Chem., 30, 1320 (1965).

D-3-(3-nitrophenyl)alanine: Pept. Res.), 3, 176 (1990).

DL-1-aminopentanesulfonic acid: European Laid-open Patent Publication No. 33504.

D-1-aminopentylphosphonic acid diethyl ester: synthesized in the same manner described in Liebigs Ann. Chem., 45 (1987).

D-(7-benzyloxy)tryptophan: synthesized in the same manner described in Tetrahedron Letters, 30, 4073 (1989).

(R)-5-(1-aminopentyl)-1H-tetrazole hydrochloride: synthesized in the same manner described in J. Org. Chem., 56, 2395 (1991).

The chemical structures, Example Nos. and compound Nos. of the prepared peptide derivatives in the present invention are shown in Tables 1 to 7.

                                      TABLE 1                                      __________________________________________________________________________      ##STR8##                                                                      Exp. No.                                                                            Compd No.                                                                            A           Exp. No.                                                                            Compd No.                                                                            A                                            __________________________________________________________________________     1    1     Boc         31   31                                                                                    ##STR9##                                    4    4                                                                                     ##STR10##  32   32                                                                                    ##STR11##                                   21   21                                                                                    ##STR12##  33   33                                                                                    ##STR13##                                   22   22                                                                                    ##STR14##  34   34                                                                                    ##STR15##                                   23   23                                                                                    ##STR16##  35   35                                                                                    ##STR17##                                   24   24                                                                                    ##STR18##  36   36                                                                                    ##STR19##                                   25   25                                                                                    ##STR20##  37   37                                                                                    ##STR21##                                   26   26                                                                                    ##STR22##  38   38                                                                                    ##STR23##                                   27   27                                                                                    ##STR24##  39   39                                                                                    ##STR25##                                   28   28                                                                                    ##STR26##  44   44                                                                                    ##STR27##                                   29   29                                                                                    ##STR28##  46   46                                                                                    ##STR29##                                   30   30                                                                                    ##STR30##  47   47                                                                                    ##STR31##                                   __________________________________________________________________________

                  TABLE 2                                                          ______________________________________                                          ##STR32##                                                                     Exp.  Compd                                                                    No.   No.      A              R.sup.3                                          ______________________________________                                         14    14       Boc            (CH.sub.2).sub.3 CH.sub.3                        15    15       Boc            CH.sub.2 C(CH.sub.3).sub.3                       40    40                                                                                       ##STR33##     CH.sub.2 C(CH.sub.3).sub.3                       41    41                                                                                       ##STR34##     CH.sub.2 Ph                                      42    42                                                                                       ##STR35##                                                                                     ##STR36##                                       43    43                                                                                       ##STR37##     CH(CH.sub.3).sub.2                               62    67                                                                                       ##STR38##     CH(CH.sub.3).sub.2                               63    68                                                                                       ##STR39##                                                                                     ##STR40##                                       64    69                                                                                       ##STR41##                                                                                     ##STR42##                                       65    70                                                                                       ##STR43##                                                                                     ##STR44##                                       ______________________________________                                    

                                      TABLE 3                                      __________________________________________________________________________      ##STR45##                                                                     Exp. No.                                                                            Compd No.                                                                            A           *  R.sup.5                                              __________________________________________________________________________     3    3     Boc         (R)                                                                                ##STR46##                                           5    5                                                                                     ##STR47##  (R)                                                                                ##STR48##                                           16   16    Boc         (R)                                                                                ##STR49##                                           17   17    Boc         (RS)                                                                               ##STR50##                                           18   18                                                                                    ##STR51##  (R)                                                                                ##STR52##                                           19   19                                                                                    ##STR53##  (RS)                                                                               ##STR54##                                           20   20                                                                                    ##STR55##  (RS)                                                                               ##STR56##                                           __________________________________________________________________________

                  TABLE 4                                                          ______________________________________                                          ##STR57##                                                                     Exp.   Compd                                                                   No.    No.         R.sup.6       Y                                             ______________________________________                                         2      2           (CH.sub.2).sub.2 CH.sub.3                                                                    COOH                                          6      6           (CH.sub.2).sub.2 SCH.sub.3                                                                   COOH                                          7      7           CH.sub.2 SCH.sub.3                                                                           COOH                                          8      8           CH.sub.2 SCH.sub.2 CH.sub.3                                                                  COOH                                          9      9           CH.sub.2 S(CH.sub.2).sub.2 CH.sub.3                                                          COOH                                          10     10          CH.sub.2 CHCH.sub.2                                                                          COOH                                          11     11          CH.sub.2 CH(CH.sub.3).sub.2                                                                  COOH                                          12     12                                                                                          ##STR58##    COOH                                          13     13          (CH.sub.2).sub.3 CH.sub.3                                                                    CH.sub.2 OH                                   45     45          CH.sub.2 CH.sub.3                                                                            COOH                                          60     65          CH.sub.2 OH   COOH                                          66     71          CH.sub.2 OCH.sub.3                                                                           COOH                                          ______________________________________                                    

                                      TABLE 5                                      __________________________________________________________________________      ##STR59##                                                                     Exp.                                                                              Comp                                                                        No.                                                                               No. A           B    R.sup.3   X.sup.1                                                                           X.sup.2                                                                          R.sup.5                                                                               Y                                __________________________________________________________________________     48 48                                                                                  ##STR60##  NH   CH.sub.2 CH(CH.sub.3).sub.2                                                              NH O (CH.sub.2).sub.3 CH.sub.3                                                             COO.sup.t Bu                     48 49                                                                                  ##STR61##  NH   CH.sub.2 CH(CH.sub.3).sub.2                                                              NH O (CH.sub.2).sub.3 CH.sub.3                                                             COOH                             49 50                                                                                  ##STR62##  NH   CH.sub.2 CH(CH.sub.3).sub.2                                                              NH O (CH.sub.2).sub.2 CH.sub.3                                                             COOH                             50 51                                                                                  ##STR63##  NH   CH.sub.2 CH(CH.sub.3).sub.3                                                              NH O (CH.sub.2).sub.2 CH.sub.3                                                             COOH                             51 52                                                                                  ##STR64##  NH                                                                                   ##STR65##                                                                               NH O (CH.sub.2).sub.3 CH.sub.3                                                             COOH                             52 53                                                                                  ##STR66##  NH                                                                                   ##STR67##                                                                               NH O (CH.sub.2).sub.3 CH.sub.3                                                             COOH                             53 54                                                                                  ##STR68##  NH   C(CH.sub.3).sub.3                                                                        NH O (CH.sub.2).sub.3 CH.sub.3                                                             COOH                             54 55                                                                                  ##STR69##  O    CH.sub.2 CH(CH.sub.3).sub.2                                                              NH O (CH.sub.2).sub.3 CH.sub.3                                                             COOH                             55 56  Boc         NH   CH.sub.2 CH(CH.sub.3).sub.2                                                              NH O CH(CH.sub.3).sub.2                                                                    COOH                             56 57                                                                                  ##STR70##  NH   CH.sub.2 C(CH.sub.3).sub.3                                                               NH S (CH.sub.2).sub.3 CH.sub.3                                                             COO.sup.t Bu                     56 58                                                                                  ##STR71##  NH   CH.sub.2 C(CH.sub.3).sub.3                                                               NH S (CH.sub.2).sub.3 CH.sub.3                                                             COOH                             57 59                                                                                  ##STR72##  NH   CH.sub.2 C(CH.sub.3).sub.3                                                               O  O (CH.sub.2).sub.3 CH.sub.3                                                             COOH                             58 60                                                                                  ##STR73##  NH   CH.sub.2 C(CH.sub.3).sub.3                                                               NH O (CH.sub.2).sub.3 CH.sub.3                                                             COO.sup.t Bu                     61 66                                                                                  ##STR74##  NH   CH.sub.2 C(CH.sub.3).sub.3                                                               NH O (CH.sub.2).sub.3 CH.sub.3                                                             COOH                             __________________________________________________________________________

                                      TABLE 6                                      __________________________________________________________________________      ##STR75##                                                                     Exp. No.                                                                            Compd No.                                                                            A        R.sup.5           Y                                        __________________________________________________________________________     59   61                                                                                    ##STR76##                                                                               ##STR77##        COOH                                     59   62                                                                                    ##STR78##                                                                               ##STR79##        COOH                                     59   63                                                                                    ##STR80##                                                                               ##STR81##        COOH                                     59   64                                                                                    ##STR82##                                                                               ##STR83##        COOH                                     67   72                                                                                    ##STR84##                                                                               ##STR85##        COOH                                     67   73                                                                                    ##STR86##                                                                               ##STR87##        COOH                                     67   74                                                                                    ##STR88##                                                                               ##STR89##        COOH                                     67   75                                                                                    ##STR90##                                                                               ##STR91##        COOH                                     68   76                                                                                    ##STR92##                                                                               ##STR93##        COO.sup.t Bu                             68   77                                                                                    ##STR94##                                                                               ##STR95##        COOH                                     69   78                                                                                    ##STR96##                                                                               ##STR97##        COOH                                     69   79                                                                                    ##STR98##                                                                               ##STR99##        COOH                                     70   80                                                                                    ##STR100##                                                                              ##STR101##       COOH                                     70   81                                                                                    ##STR102##                                                                              ##STR103##       COOH                                     70   82                                                                                    ##STR104##                                                                              ##STR105##       COOH                                     70   83                                                                                    ##STR106##                                                                              ##STR107##       COOH                                     74   87                                                                                    ##STR108##                                                                              ##STR109##       CH.sub.2 OH                              74   88                                                                                    ##STR110##                                                                              ##STR111##       CH.sub.2 OH                              87   102                                                                                   ##STR112##                                                                              ##STR113##       COOH                                     88   103                                                                                   ##STR114##                                                                              ##STR115##       COOH                                     89   104                                                                                   ##STR116##                                                                              ##STR117##       COOH                                     __________________________________________________________________________

                                      TABLE 7                                      __________________________________________________________________________      ##STR118##                                                                    Exp. No.                                                                            Compd No.                                                                            R.sup.3  R.sup.6      *  Y                                          __________________________________________________________________________     71   84    CH.sub.2 C(CH.sub.3).sub.3                                                              (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                               COOMe                                      72   85    CH.sub.2 C(CH.sub.3).sub.3                                                              (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                               COOEt                                      73   86    CH.sub.2 C(CH.sub.3).sub.3                                                              (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                               COO.sup.i Pr                               75   89                                                                                    ##STR119##                                                                             (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                               COO.sup.t Bu                               75   90                                                                                    ##STR120##                                                                             (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                               COOH                                       76   91                                                                                    ##STR121##                                                                             CH.sub.3     (R)                                                                               CH.sub.2 COOH                              77   92    CH.sub.2 C(CH.sub.3).sub.3                                                              H            -- COOH                                       78   93    CH.sub.2 C(CH.sub.3).sub.3                                                              H            -- CH.sub.2 COOH                              81   96    CH.sub.2 C(CH.sub.3).sub.3                                                              H            -- SO.sub.3 H                                 79   94    CH.sub.2 C(CH.sub.3).sub.3                                                               ##STR122##  (R)                                                                               COOH                                       80   95    CH.sub.2 C(CH.sub.3).sub.3                                                              (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                               CH.sub.2 COOH                              82   97    CH.sub.2 C(CH.sub.3).sub.3                                                              H            -- CH.sub.2 SO.sub.3 H                        83   98    CH.sub.2 C(CH.sub.3).sub.3                                                              (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                               CH.sub.2 SO.sub.3 H                        84   99    CH.sub.2 C(CH.sub.3).sub.3                                                              (CH.sub.2).sub.3 CH.sub.3                                                                   (RS)                                                                              SO.sub.3 H                                 85   100   CH.sub.2 C(CH.sub.3).sub.3                                                              (CH.sub.2).sub.3 CH.sub.3                                                                   (S)                                                                               PO.sub.3 H.sub.2                           86   101   CH.sub.2 C(CH.sub.3).sub.3                                                              (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                               CONHCH.sub.2 CH.sub.2 OH                   90   105   CH.sub.2 C(CH.sub.3).sub.3                                                              (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                                ##STR123##                                91   106   CH(CH.sub.3).sub.2                                                                      (CH.sub.2).sub.3 CH.sub.3                                                                   (RS)                                                                              SO.sub.3 H                                 92   107   CH(CH.sub.3).sub.2                                                                      (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                               CH.sub.2 SO.sub.3 H                        93   108   CH.sub.2 CH(CH.sub.3).sub.2                                                             (CH.sub.2).sub.3 CH.sub.3                                                                   (R)                                                                               CH.sub.2 SO.sub.3 H                        94   109   CH.sub.2 CH(CH.sub.3).sub.2                                                             (CH.sub.2).sub.3 CH.sub.3                                                                   (RS)                                                                              SO.sub.3 H                                 __________________________________________________________________________

Now, the endothelin antagonistic properties of the peptide derivatives of the present invention will be described.

Endothelin Binding Inhibition Test

The cerebellum of porcine was homogenized in a buffer solution of 10 mM MOPS, pH 7.4, at 4° C. by a polytron. To the homogenate, sucrose was added to a concentration of 20%, and the mixture was centrifuged at 1,000×g for 15 minutes, and the supernatant was further centrifuged at 10,000×g for 15 minutes. The supernatant thereof was further centrifuged at 90,000×g for 40 minutes. The membrane precipitate thereby obtained was suspended in a buffer solution of 5 mM HEPES/Tris, pH 7.4, at a concentration of 3.3 mg/ml.

Then, 16 μl of this membrane suspension was added to 340 μl of 50 mM tris/HCl buffer, pH 7.4, containing 10 μl calcium chloride, 10 μM magnesium chloride, 0.1 mM PMSF, 1 μM pepstatin A, 2 μM leupeptin, 1 mM 1,10-phenanthroline and 0.1% bovine serum albumin. To this suspension, 4 μl of (A) endothelin-1 (for nonspecific binding; 0.2 μM as the final concentration), (B) buffer solution A (for total control binding), or (C) a test compound (1.1 μM as the final concentration), was added. Further, to each suspension, 40 μl of ¹²⁵ I-endothelin-1 (12000-18000 cpm) was added. These mixtures were incubated at 25° C. for 4 hours, then subjected to filtration on a glass filter GF/C and then washed with 5 mM HEPES/Tris, pH 7.4, containing 0.3% bovine serum albumin. Then, the radioactivity trapped by the glass filter was measured, and the ¹²⁵ I-endothelin-1 binding inhibition D (%) at 1.1 μM of the test compound was determined by the following equation. ##EQU1## Each test was performed in triplicate.

                  TABLE 8                                                          ______________________________________                                         .sup.125 I-endothelin-1 binding inhibition by                                  1.1 μM of the test compound                                                       Inhi-           Inhi-       Inhi-       Inhi-                                  bi-             bi-         bi-         bi-                              Compd ition  Compd    tion Compd  tion Compd  tion                             No.   (%)    No.      (%)  No.    (%)  No.    (%)                              ______________________________________                                         1     90     28       99   55     100  83     57                               2     84     29       89   56     70   84     98                               3     75     30       73   57     89   85     98                               4     99     31       96   58     98   86     94                               5     97     32       72   59     95   87     99                               6     64     33       99   60     95   88     96                               7     78     34       99   61     64   89     96                               8     81     35       97   62     75   90     100                              9     54     36       95   63     82   91     94                               10    81     37       90   64     77   92     59                               11    41     38       84   66     91   93     80                               12    77     39       98   67     100  94     86                               13    26     40       99   68     100  95     100                              14    65     41       67   69     100  96     51                               15    89     42       97   70     100  97     58                               16    18     43       99   71     60   98     98                               17    18     44       97   72     86   99     99                               18    94     45       71   73     35   100    96                               19    61     46       91   74     44   101    98                               20    75     47       35   75     42   102    92                               21    94     48       92   76     33   103    94                               22    93     49       99   77     69   104    74                               23    100    50       99   78     84   105    100                              24    97     51       99   79     96   106    100                              25    88     52       100  80     94   107    100                              26    85     53       100  81     18   108    99                               27    83     54       97   82     50   109    99                               ______________________________________                                    

As shown in Table 8, the compounds of the present invention were found to be very potent inhibitor of endothelin binding to ET_(B) receptor. The test compounds are indicated by compound Nos.

On the other hand, each of the representative compounds (Reference Compounds 1, 2 and 3) of the endothelin antagonistic peptides described in EP 0460679A2 showed, at a concentration of 1.1 μM, 69, 77 or 86% of the ¹²⁵ I-ET-1 binding inhibition to porcine aorta membrane suspension containing a large amount of ET_(A) receptors, and, on the contrary, only 6.4, 3.8 or 10.1% of the ¹²⁵ I-ET-1 binding inhibition to ET_(B) receptors of porcine cerebellum membrane suspension used in the present experiments. ##STR124##

Activities Against Endothelin-Induced Contraction of Isolated Rabbit Pulmonary Arteries

The pulmonary artery of rabbit was isolated, and a spiral preparation having a width of 1 mm and a length of 10 mm was prepared therefrom. The preparation having the endothelial cells denuded, was placed in a 5 ml organ bath filled with a Krebs.Henseleit solution saturated with a gas mixture of 95% O₂ and 5% CO₂, and a change in the tension was isometrically measured and recorded.

Endothelin-3 was added into the organ bath in a cumulatively increasing manner, whereby the influence of a compound of the present invention to the concentration-response curve for endothelin-3 was examined. The compound was added into the organ bath 20 minutes prior to the addition of endothelin-3.

As shown in FIGS. 1 to 3, Compound 4, Compound 39 and Compound 40 (0.1 to 10 μM) remarkably shifted the concentration-response curves of endothelin-3 to the right. Table 9 shows pA₂ values (-log of the concentration of the compound necessary for shifting the concentration-response curve for endothelin-3 twice to the right. Further, the compounds showed no effects to the isolated pulmonary artery when applied alone. As is evident from the above, the compounds showed remarkable antagonistic activities against endothelin-induced concentration of isolated rabbit pulmonary artery.

                  TABLE 9                                                          ______________________________________                                         Antagonistic activities of the compound of the                                 present invention against endothelin-3-induced                                 contraction of isolated rabbit pulmonary artery                                Compound No.    PA.sub.2 value                                                 ______________________________________                                         4               6.7                                                            39              6.7                                                            40              7.1                                                            ______________________________________                                    

Activities Against Endothelin-Induced Contraction of Isolated Guinea Pig Bronchus

The bronchus of a guinea pig was isolated, and the bronchus was cut into rings having an outer diameter of 2 mm and a width of 4 mm to afford a preparation. The preparation was placed in a 5 ml organ bath filled with a Krebs.Henseleit solution saturated with a gas mixture of 95% O₂ and 5% CO₂, and a change in the tension was isometrically measured and recorded.

Endothelin-3 was added into the organ bath in a cumulatively increasing manner, and the influence of a compound of the present invention to the concentration-response curve for endothelin was examined. The compound was added into the organ bath 20 minutes prior to the addition of endothelin-3.

As shown in FIGS. 1 to 3, Compound 4, Compound 39 and Compound 40 (10 μM) remarkably shifted to concentration-response curves for endothelin-3 to the right in isolated bronchus. Further, the compounds showed no effects to the isolated bronchus when applied alone. As is evident from the foregoing, the compounds showed remarkable antagonistic activities against endothelin-induced contraction of isolated guinea pig bronchus.

Thus, the compounds of the present invention have excellent endothelin antagonistic activities and are useful as vasodilators for bronchodilators in the field of medicines, and they can be drugs for treating hypertension, pulmonary hypertension, Raynaud's disease, acute renal failure, myocardial infarction, angina pectoris, cerebral infarction, cerebral vasospasm, arteriosclerosis, asthma, gastric ulcer, diabetes, endotoxin shock endotoxin-induced multiple organ failure or disseminated intravascular coagulation, and/or cyclosporin-induced renal failure or hypertension. When used as drugs for treating such diseases, the compounds of the present invention can be used alone or in combination with other drugs for treatment.

The compounds of the present invention may be used in the form of drug formulations suitable for parenteral administration, oral administration or external administration by mixing them with solid or liquid excipient carriers known in this field. The drug formulations include a liquid formulation such as an injection formulation, an inhalant formulation, a syrup formulation or an emulsion, a solid formulation such as tablets, capsules or granules, and an external drug such as an ointment or a suppository. Further, these drug formulations may contain additives which are commonly employed, such as an adjuvant, a stabilizer, a wetting agent, an emulsifier, an absorption-promoting agent or a surfactant, as the case requires. As the additives, distilled water for injection, physiological saline, Ringer's solution, glucose, sugar syrup, gelatin, vegetable oil, cacao butter, ethylene glycol, hydroxypropyl cellulose, lactose, sucrose, corn starch, magnesium stearate and talc may be mentioned.

The dose of a compound of the present invention as an endothelin antagonist varies depending upon the manner of administration, the age and body weight of the patient and the condition of the patient to be treated. However, a typical administration method for an adult is oral administration or parenteral administration. The daily dose in the case of oral administration to an adult patient is from 0.1 to 100 mg/kg body weight, and the daily dose in the case of parenteral administration is from 0.01 to 10 mg/kg body weight.

The following Examples and Referential Examples illustrate the present invention more specifically. It should be understood that the present invention is not limited to these examples alone.

EXAMPLE 1 Synthesis of Compound 1 (1) Preparation of Boc-Leu-DTrp(COOMe)-OH

To a mixture of Boc-Leu-OH.H₂ O (2.5 g), H-DTrp-OBzl (2.9 g) and HOBT.H₂ O (1.6 g) in dichloromethane (50 ml) was added EDCI.HCl (2.0 g) under ice cooling. After being stirred at room temperature for 16 h, the mixture was washed with water, 10% aq. citric acid, sat. aq. NaHCO₃ and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was triturated with hexane to give Boc-Leu-DTrp-OBzl (4.79 g). To a solution of the dipeptide (753 mg) in dichloromethane (7 ml) were added methyl chloroformate (1 ml), pulverized NaOH (89 mg) and TBAHS (20 mg) under ice cooling. After being stirred of the mixture at room temperature for 30 min, pulverized NaOH (89 mg) was added. This procedure was repeated twice more. The reaction mixture was diluted with dichloromethane, washed with sat. aq. NaHCO₃, 10% aq. citric acid, water and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was recrystallized from dichloromethane and petroleum ether to give Boc-Leu-DTrp(COOMe)-OBzl (721 mg) as colorless crystals. The dipeptide (708 mg) was dissolved in methanol (7 ml)--THF (5 ml) and 10% Pd/C (70 mg) was added. The mixture was vigorously stirred at room temperature under an atmospheric pressure of hydrogen for 1 h. The reaction mixture was filtered and the filtrate was evaporated in vacuo to give Boc-Leu-DTrp(COOMe)-OH (580 mg).

FAB-MS (m/e, (C₂₄ H₃₃ N₃ O₇ +H)⁺): 476

(2) Preparation of Boc-Leu-DTrp(COOMe)-DNle-OBzl

To a mixture of Boc-Leu-DTrp(COOMe)-OH (50 mg), H-DNle-OBzl.TsOH (46 mg), NMM (13 μl) and HOBT.H₂ O (16 mg) in dichloromethane (1 ml) was added EDCI.HCl (22 mg) under ice cooling. After being stirred at room temperature for 2 h, the mixture was diluted with dichloromethane, washed with water, 10% aq. citric acid, sat. aq. NaHCO₃ and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol/acetic acid=100/10/1 for development to give Boc-Leu-DTrp(COOMe)-DNle-OBzl (67 mg).

FAB-MS (m/e, (C₃₇ H₅₀ N₄ O₈ +H)⁺): 679

(3) Preparation of Compound 1

A solution of Boc-Leu-DTrp(COOMe)-DNle-OBzl (25 mg) in methanol (1 ml) was hydrogenated over 10% Pd/C at an atmospheric pressure of hydrogen for 1 h. After removal of the catalyst by filtration, the filtrate was concentrated in vacuo. The residue was purified by preparative TLC (3M, Empore Silica Sheet) with chloroform/methanol/acetic acid=100/10/1 for development and the product was reprecipitated from methanol and water to give Compound 1 (11 mg).

m.p.: 154°-163° C.

IR (KBr, cm⁻): 3328, 2962, 2872, 1728, 1695, 1650, 1536, 1461, 1386, 1371, 1341, 1311, 1260, 1167, 1092, 762, 747

High Resolution FAB-MS (m/e, (C₃₀ H₄₄ N₄ O₈ +H)⁺): Calcd: 589,3237 Found: 589,3260

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (6H, d, J=6.2 Hz), 0.85 (3H, t, J=7.0 Hz), 0.93-1.10 (2H, m), 1.10-1.55 (5H, m), 1.31 (9H, s), 1.55-1.82 (2H, m), 2.86 (1H, dd, J=10.6 Hz, 15.2 Hz), 3.00-3.30 (1H, m), 3.80-3.90 (1H, m), 3.95 (3H, s), 4.05-4.20 (1H, m), 4.59-4.70 (1H, m), 6.74 (1H, d, J=7.1 Hz), 7.23 (1H, t, J=7.5 Hz), 7.31 (1H, t, J=7.5 Hz), 7.49 (1H, s), 7.70 (1H, d, J=7.5 Hz), 8.04 (2H, d, J=7.5 Hz), 8.20 (1H, d, J=8.3 Hz)

EXAMPLE 2 Synthesis of Compound 2

Compound 2 was prepared using H-DNle-OBzl.TsOH as a starting material in the same manner described in Example 1-(2) and (3).

m.p.: 179°-185° C.

IR (KBr, cm⁻¹): 3322, 2968, 1720, 1656, 1530, 1461, 1389, 1341, 1311, 1260, 1167, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₂₉ H₄₂ N₄ O₈ +H)⁺): Calcd: 575.3080 Found: 575.3101

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (3H, d, J=7.2 Hz), 0.66 (3H, d, J=7.2 Hz), 0.85 (3H, t, J=7.2 Hz), 0.95-1.75 (7H, m), 1.31 (9H, s), 2.88 (1H, dd, J=10.6 Hz, 14.9 Hz), 3.15 (1H, dd, J=4.3 Hz, 14.9 Hz), 3.85 (1H, m), 3.95 (3H, s), 4.06 (1H, dt, J=5.6 Hz, 7.6 Hz), 4.61 (1H, ddd, J=4.3 Hz, 7.6 Hz, 10.6 Hz), 6.72 (1H, d, J=7.6 Hz), 7.23 (1H, t, J=7.6 Hz), 7.31 (1H, t, J=7.6 Hz), 7.48 (1H, s), 7.69 (1H, d, J=7.6 Hz), 7.93 (1H, d, J=7.6 Hz), 8.03 (1H, d, J=7.6 Hz), 8.19 (1H, d, J=8.4 Hz)

EXAMPLE 3 Synthesis of Compound 3 (1) Preparation of Boc-Leu-DTrp(COOEt)-DNle-OBzl

The title compound was prepared using ethyl chloroformate instead of methyl chloroformate in the same manner described in Example 1-(1) and (2).

FAB-MS (m/e, (C₃₈ H₅₂ N₄ O₈ +H)⁺): 693

(2) Preparation of Compound 3

Compound 3 was prepared using Boc-Leu-DTrp(COOEt)-DNle-OBzl as a starting material in the same manner described in Example 1-(3).

m.p.: 104°-105° C.

IR (KBr, cm⁻¹): 3322, 2968, 2872, 1720, 1662, 1536, 1461, 1386, 1254, 1170, 747

High Resolution FAB-MS (m/e, (C₃₁ H₄₆ N₄ O₈ +H)⁺): Calcd: 603.3394 Found: 603.3406

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (6H, d, J=6.4 Hz), 0.77-1.90 (12H, m), 1.31 (9H, s), 1.37 (3H, t, J=7.0 Hz), 2.88 (1H, dd, J=10.7 Hz, 15.4 Hz), 3.15 (1H, dd, J=4.2 Hz, 15.4 Hz), 3.80-3.91 (1H, m), 4.05-4.25 (1H, m), 4.40 (2H, q, J=7.0 Hz), 4.60-4.71 (1H, m), 6.73 (1H, d, J=7.6 Hz), 7.23 (1H, t, J=7.5 Hz), 7.31 (1H, t, J=7.5 Hz), 7.51 (1H, s), 7.70 (1H, d, J=7.5 Hz), 8.03 (1H, d, J=7.5 Hz), 8.06 (1H, brs), 8.19 (1H, d, J=8.8 Hz)

EXAMPLE 4 Synthesis of Compound 4

A mixture of Boc-Leu-DTrp(COOMe)-DNle-OBzl (20 mg, prepared in Example 1-(2)) in TFA (0.5 ml) was stirred under ice cooling for 15 min and evaporated in vacuo. To a solution of the residue in chloroform (0.5 ml) were added TEA (6 μl) and 2-chlorophenylisocyanate (4 μl) under ice cooling. After being stirred at the same temperature for 1 h, the mixture was diluted with chloroform, washed with 1N-hydrochloric acid, 5% aq. NaHCO₃, and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol=50/1 for development, and the product was hydrogenated over 10% Pd/C at an atmospheric pressure of hydrogen for 1 h. The reaction mixture was filtered and the filtrate was evaporated in vacuo. The residue was purified by reverse phase MPLC (Merck, LiChroprep RP-18) with methanol/water=5/1 for elution to give Compound 4 (5 mg) .

m.p.: 193°-201° C.

IR (KBr, cm⁻¹): 3328, 2962, 2872, 1740, 1647, 1593, 1548, 1461, 1446, 1386, 1341, 1311, 1263, 1230, 1092, 747

High Resolution FAB-MS (m/e, (C₃₂ H₄₀ ClN₅ O₇ +H)⁺): Calcd: 642.2695 Found: 642.2661

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (3H, d, J=5.8 Hz), 0.67 (3H, d, J=5.8 Hz), 0.82 (3H, t, J=7.1 Hz), 1.00-1.40 (7H, m), 1.57-1.80 (2H, m), 2.89 (1H, dd, J=3.2 Hz, 11.5 Hz), 3.10-3.20 (1H, m), 3.95 (3H, s), 4.08-4.22 (2H, m), 4.62-4.72 (1H, m), 6.91 (1H, dt, J=1.4 Hz, 7.8 Hz), 7.14-7.32 (4H, m), 7.35 (1H, dd, J=1.4 Hz, 7.8 Hz), 7.54 (1H, s), 7.76 (1H, d, J=7.8 Hz), 8.05 (1H, d, J=7.8 Hz), 8.08 (1H, dd, J=1.4 Hz, 7.8 Hz), 8.11 (1H, s), 8.13-8.20 (1H, m), 8.50 (1H, d, J=8.5 Hz)

EXAMPLE 5 Synthesis of Compound 5

Compound 5 prepared was using Boc-Leu-DTrp(COOEt)-DNle-OBzl as a starting material in the same manner described in Example 4.

m.p.: 161°-168° C.

IR (KBr, cm⁻¹): 3328, 2962, 2872, 1740, 1644, 1593, 1551, 1461, 1446, 1206, 1092, 747

High Resolution FAB-MS (m/e, (C₃₃ H₄₂ ClN₅ O₇ +H)⁺): Calcd: 656.2852 Found: 656.2851

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (3H, d, J=6.4 Hz), 0.66 (3H, d, J=6.4 Hz), 0.82 (3H, t, J=7.2 Hz), 0.88-1.80 (9H, m), 1.38 (3H, t, J=7.0 Hz), 2.90 (1H, dd, J=11.8 Hz, 14.4 Hz), 3.15 (1H, dd, J=2.7 Hz, 14.4 Hz), 4.10-4.25 (2H, m), 4.41 (2H, q, J=7.0 Hz), 4.64-4.75 (1H, m), 6.86 (1H, s), 6.91 (1H, dt, J=1.6 Hz, 7.6 Hz), 7.12-7.40 (5H, m), 7.56 (1H, s), 7.75 (1H, d, J=7.1 Hz), 8.05 (1H, d, J=7.1 Hz), 8.09 (1H, d, J=10.1 Hz), 8.17 (1H, d, J=7.9 Hz), 8.47 (1H, d, J=8.8 Hz)

EXAMPLE 6 Synthesis of Compound 6

To a solution of Boc-Leu-DTrp(COOMe)-OH (104 mg, prepared in Example 1-(1)) in DMF (3.5 ml) were added HOSu (51 mg) and EDCI.HCl (64 mg) under ice cooling. The mixture was stirred at the same temperature for 1.5 h and at room temperature for 5 h. To the mixture was added an aqueous solution of H-DMet-ONa (prepared from DMet (49 mg) and sodium bicarbonate (28 mg) in water (2 ml)) under ice cooling. After being stirred at room temperature for 2 h, the reaction mixture was diluted with ethyl acetate, washed with 10% aq. citric acid and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by reverse phase chromatography (Nacalai Tesque, Cosmosil 75C18-OPN) with methanol/water=7/3-8/2 for elution to give Compound 6 (65 mg).

m.p.: 140°-143° C.

IR (KBr, cm⁻¹): 3322, 2962, 1740, 1653, 1533, 1461, 1389, 1341, 1260, 1167, 1092, 762, 747

High Resolution FAB-MS (m/e, (C₂₉ H₄₂ N₄ O₈ S+H)⁺): Calcd: 607.2801 Found: 607.2761

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (6H, d, J=5.9 Hz), 1.00-1.25 (3H, m), 1.32 (9H, s), 1.85-2.05 (2H, m), 2.04 (3H, s), 2.52-2.75 (2H, m), 2.87 (1H, dd, J=10.7 Hz, 15.4 Hz), 3.16 (1H, dd, J=6.2 Hz, 15.4 Hz), 3.78-3.85 (1H, m), 3.95 (3H, s), 4.28-4.37 (1H, m), 4.59-4.70 (1H, m), 6.79 (1H, d, J=7.6 Hz), 7.25 (1H, t, J=7.6 Hz), 7.32 (1H, t, J=7.6 Hz), 7.50 (1H, s), 7.69 (1H, d, J=7.6 Hz), 8.04 (1H, d, J=7.6 Hz), 8.11 (1H, d, J=8.4 Hz), 8.22 (1H, d, J=8.3 Hz)

Each Compound 7-12 described in the following Examples 7-12 was prepared using each corresponding amino acid sodium salt as a starting material in the same manner described in Example 6.

EXAMPLE 7 Compound 7

m.p.: 147°-150° C.

IR (KBr, cm⁻¹): 3334, 2962, 1740, 1650, 1553, 1461, 1386, 1341, 1311, 1260, 1167, 1092, 767, 747

High Resolution FAB-MS (m/e, (C₂₈ H₄₀ N₄ O₈ S+H)⁺): Calcd: 593.2645 Found: 593.2628

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (3H, d, J=6.3 Hz), 0.66 (3H, d, J=5.4 Hz), 0.70-1.15 (3H, m), 1.31 (9H, s), 2.09 (3H, s), 2.75-2.92 (3H, m), 3.15 (1H, dd, J=3.5 Hz, 14.9 Hz), 3.85-3.94 (1H, m), 3.95 (3H, s), 4.42 (1H, dt, J=5.0 Hz, 7.6 Hz), 4.64-4.73 (1H, m), 6.72 (1H, d, J=7.6 Hz), 7.24 (1H, t, J=7.4 Hz), 7.31 (1H, t, J=7.4 Hz), 7.50 (1H, s), 7.72 (1H, d, J=7.4 Hz), 8.04 (1H, d, J=7.4 Hz), 8.20 (1H, d, J=8.5 Hz), 8.36 (1H, d, J=7.8 Hz)

EXAMPLE 8 Compound 8

m.p.: 170°-173° C.

IR (KBr, cm⁻¹): 3346, 2968, 1743, 1650, 1611, 1530, 1461, 1389, 1341, 1260, 1170, 1092, 762, 747

High Resolution FAB-MS (m/e, (C₂₉ H₄₂ N₄ O₈ S+H)⁺): Calcd: 607.2802 Found: 607.2792

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (3H, d, J=6.4 Hz), 0.67 (3H, d, J=3.9 Hz), 0.70-1.20 (3H, m), 1.16 (3H, t, J=7.3 Hz), 1.31 (9H, s), 2.53 (2H, q, J=7.3 Hz), 2.78-2.97 (3H, m), 3.14 (1H, dd, J=3.6 Hz, 14.7 Hz), 3.82-3.96 (1H, m), 3.95 (3H, s), 4.36 (1H, dt, J=5.4 Hz, 7.8 Hz), 4.62-4.75 (1H, m), 6.69 (1H, d, J=7.8 Hz), 7.24 (1H, t, J=7.3 Hz), 7.31 (1H, t, J=7.3 Hz), 7.50 (1H, s), 7.72 (1H, d, J=7.3 Hz), 8.03 (1H, d, J=7.3 Hz), 8.18 (1H, d, J=8.9 Hz), 8.31 (1H, d, J=7.9 Hz)

EXAMPLE 9 Compound 9

m.p.: 106°-108° C.

IR (KBr, cm⁻¹): 3322, 2968, 1737, 1695, 1653, 1530, 1461, 1386, 1341, 1311, 1260, 1167, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₀ H₄₄ N₄ O₈ S+H)⁺): Calcd: 621.2958 Found: 621.2938

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (3H, d, J=6.4 Hz), 0.66 (3H, d, J=6.4 Hz), 0.91 (3H, t, J=7.3 Hz), 0.98-1.28 (3H, m), 1.31 (9H, s), 1.52 (2H, sext, J=7.3 Hz), 2.48-2.53 (2H, m), 2.75-2.95 (3H, m), 3.15 (1H, dd, J=4.2 Hz, 15.4 Hz), 3.85-3.94 (1H, m), 3.95 (3H, s), 4.32-4.40 (1H, m), 4.65-4.72 (1H, m), 6.70 (1H, d, J=7.8 Hz), 7.24 (1H, t, J=7.4 Hz), 7.31 (1H, t, J=7.4 Hz), 7.50 (1H, s), 7.72 (1H, d, J=7.4 Hz), 8.04 (1H, d, J=7.4 Hz), 8.18 (1H, d, J=8.3 Hz), 8.33 (1H, d, J=7.0 Hz)

EXAMPLE 10 Compound 10

m.p.: 188°-190° C.

IR (KBr, cm⁻¹): 3304, 2962, 1740, 1653, 1533, 1461, 1386, 1341, 1260, 1167, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₂₉ H₄₀ N₄ O₈ +H)⁺): Calcd: 573.2924 Found: 573.2919

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (6H, d, J=6.1 Hz), 0.94-1.30 (3H, m), 1.32 (9H, s), 2.37-3.52 (2H, m), 2.87 (1H, dd, J=10.7 Hz, 15.4 Hz), 3.16 (1H, dd, J=4.2 Hz, 15.4 Hz), 3.82-3.90 (1H, m), 3.95 (3H, s), 4.24-4.31 (1H, m), 4.60-4.72 (1H, m), 5.05 (1H, dd, J=1.7 Hz, 9.8 Hz), 5.12 (1H, dd, J=1.7 Hz, 17.7 Hz), 5.72-5.85 (1H, m), 6.75 (1H, d, J=7.6 Hz), 7.24 (1H, t, J=7.3 Hz), 7.32 (1H, t, J=7.3 Hz), 7.50 (1H, s), 7.70 (1H, d, J=7.3 Hz), 8.04 (1H, d, J=7.3 Hz), 8.16 (1H, d, J=8.7 Hz), 8.20 (1H, d, J=8.5 Hz)

EXAMPLE 11 Compound 11

m.p.: 99°-126° C. (dec.)

IR (KBr, cm⁻¹): 3304, 2962, 1740, 1656, 1553, 1461, 1389, 1260, 1167, 1092, 1047, 765, 747

High Resolution FAB-MS (m/e, (C₃₀ H₄₄ N₄ O₈ +H)⁺): Calcd: 589.3273 Found: 589.3243

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.66 (3H, d, J=6.4 Hz), 0.67 (3H, d, J=6.4 Hz), 0.70-1.73 (12H, m), 1.31 (9H, s), 2.88 (1H, dd, J=10.7 Hz, 15.4 Hz), 3.15 (1H, dd, J=4.2 Hz, 15.4 Hz), 3.82-4.00 (1H, m), 3.95 (3H, s), 4.00-4.12 (1H, m), 4.51-4.68 (1H, m), 6.69 (1H, d, J=7.6 Hz), 7.23 (1H, t, J=7.9 Hz), 7.29 (1H, t, J=7.9 Hz), 7.48 (1H, s), 7.69 (1H, d, J=7.9 Hz), 7.80 (1H, d, J=8.8 Hz), 8.03 (1H, d, J=7.9 Hz), 8.16 (1H, d, J=7.8 Hz)

EXAMPLE 12 Compound 12

m.p.: 185°-189° C.

IR (KBr, cm⁻¹): 3310, 2968, 1740, 1656, 1539, 1461, 1386, 1260, 1170, 1092, 1047, 765, 747

High Resolution FAB-MS (m/e, (C₃₀ H₄₄ N₄ O₈ +H)⁺): Calcd: 589.3237 Found: 589.3227

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (3H, d, J=6.5 Hz), 0.68 (3H, d, J=6.5 Hz), 0.79 (3H, d, J=6.8 Hz), 0.84 (3H, t, J=7.3 Hz), 0.93-1.60 (6H, m), 1.31 (9H, s), 2.92 (1H, dd, J=10.7 Hz, 15.4 Hz), 3.12 (1H, dd, J=4.2 Hz, 15.4 Hz), 3.85-4.02 (1H, m), 3.95 (3H, s), 4.06-4.17 (1H, m), 4.56-4.69 (1H, m), 6.66 (1H, d, J=8.6 Hz), 7.23 (1H, t, J=7.3 Hz), 7.30 (1H, t, J=7.3 Hz), 7.50 (1H, s), 7.53 (1H, d, J=8.5 Hz), 7.68 (1H, d, J=7.3 Hz), 8.03 (1H, d, J=7.3 Hz), 8.16 (1H, d, J=7.8 Hz)

EXAMPLE 13 Synthesis of Compound 13

To a solution of Boc-Leu-DTrp(COOMe)-OH (25 mg, prepared in Example 1-(1)) in dichloromethane (0.5 ml) were added D-norleucinol hydrochloride (12 mg), NMM (8.5 μl), HOBT.H₂ O (8 mg) and EDCI.HCl (15 mg) successively under ice cooling. The mixture was stirred at 0°-5° C. for 10 min and at room temperature for 1 h. The reaction mixture was diluted with ethyl acetate, washed with 4% aq. NaHCO₃, 10% aq. citric acid, water and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol=10/1 for development to give Compound 13 (26 mg).

m.p.: 141°-148° C.

IR (KBr, cm⁻¹): 3304, 2962, 1743, 1647, 1536, 1461, 1386, 1371, 1341, 1311, 1260, 1170, 1092, 762, 747

High Resolution FAB-MS (m/e, (C₃₀ H₄₆ N₄ O₇ +H)⁺): Calcd: 575.3444 Found: 575.3481

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.69-0.95 (9H, m), 0.96-1.70 (17H, m), 2.88 (1H, dd, J=10.5 Hz, 14.2 Hz), 3.08-3.25 (2H, m), 3.60-3.76 (1H, m), 3.76-3.88 (1H, m), 3.95 (3H, s), 4.42-4.66 (3H, m), 6.80 (1H, d, J=6.9 Hz), 7.24 (1H, t, J=7.4 Hz), 7.32 (1H, t, J=7.4 Hz), 7.48 (1H, s), 7.49 (1H, d, J=7.4 Hz), 7.67 (1H, d, J=7.4 Hz), 8.04 (1H, d, J=9.1 Hz), 8.18 (1H, d, J=8.4 Hz)

EXAMPLE 14 Synthesis of Compound 14 (1) Preparation of Boc-DTrp-DNle-OBzl

To a solution of H-DNle-OBzl.TsOH (1.27 g) in dichloromethane (20 ml) were added NMM (0.53 ml), Boc-DTrp-OH (1.22 g), HOBT.H₂ O (734 mg) and EDCI.HCl (926 mg) successively under ice cooling. The mixture was stirred at the same temperature for 1 h and at room temperature for 2 h. The mixture was diluted with ethyl acetate, washed with sat. aq. NaHCO₃, 10% aq. citric acid, and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was recrystallized from ethyl acetate and hexane to give Boc-DTrp-DNle-OBzl (1.56 g).

FAB-MS (m/e, (C₂₉ H₃₇ N₃ O₅ +H)⁺): 508

(2) Preparation of Boc-DTrp(COOMe)-DNle-OBzl

To a solution of the dipeptide obtained in (1) (1.00 g) in dichloromethane (20 ml) were added pulverized NaOH (118 mg), TBAHS (134 mg) and methyl chloroformate (228 μl) at room temperature under argon atmosphere. After being stirred at room temperature for 8 h, the reaction mixture was diluted with dichloromethane, washed with 10% aq. citric acid, sat. aq. NaHCO₃, water and brine successively, dried over MgSO₄ and evaporated in vacuo to give Boc-DTrp(COOMe)-DNle-OBzl (1.11 g).

FAB-MS (m/e, (C₃₁ H₃₉ N₃ O₇ +H)⁺): 566

(3) Preparation of Compound 14

A mixture of Boc-DTrp(COOMe)-DNle-OBzl (83 mg) in TFA (2 ml) was stirred at room temperature for 1 h and evaporated in vacuo. To a solution of the residue in DMF (0.6 ml) were added NMM (18 μl), Boc-Nle-OH (51 mg) and EDCI.HCl (43 mg) successively under ice cooling. The mixture was stirred at the same temperature for 1 h and at room temperature for 12 h. The mixture was diluted with ethyl acetate, washed with sat. aq. NaHCO₃, 10% aq. citric acid, water and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by MPLC (Merck, LiChroprep Si 60) with chloroform/methanol=500/6 for elution to give Boc-Nle-DTrp(COOMe)-DNle-OBzl (88 mg). A solution of the tripeptide derivative (22.4 mg) in methanol was hydrogenated over 10% Pd/C (10 mg) at an atmospheric pressure of hydrogen for 2 h. After removal of the catalyst by filtration, the filtrate was concentrated in vacuo. The residue was purified by preparative TLC (3M, Empore Silica Sheet) with chloroform/methanol=20/1 for development to give Compound 14 (14 mg).

m.p.: 152°-159° C.

IR (KBr, cm⁻¹): 3322, 2962, 2872, 1725, 1656, 1539, 1461, 1386, 1371, 1341, 1311, 1260, 1167, 1092, 762, 747

High Resolution FAB-MS (m/e, (C₃₀ H₄₄ N₄ O₈ +H)⁺): Calcd: 589.3237 Found: 589.3248

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.64 (3H, d, J=7.2 Hz), 0.78-1.82 (12H, m), 0.85 (3H, t, J=6.9 Hz), 1.32 (9H, s), 2.87 (1H, dd, J=10.4 Hz, 14.8 Hz), 3.10-3.30 (1H, m), 3.76-3.90 (1H, m), 3.95 (3H, s), 4.45-4.60 (1H, m), 4.60-4.72 (1H, m), 6.68 (1H, d, J=6.8 Hz), 7.24 (1H, t, J=7.4 Hz), 7.31 (1H, t, J=7.4 Hz), 7.51 (1H, s), 7.71 (1H, d, J=7.4 Hz), 8.02 (1H, d, J=7.4 Hz), 8.03 (1H, d, J=8.1 Hz), 8.18 (1H, d, J=7.8 Hz)

EXAMPLE 15 Synthesis of Compound 15

Compound 15 was prepared using Boc-γMeLeu instead of Boc-Nle in the same manner described in Example 14-(3).

m.p.: 118°-125° C.

IR (KBr, cm⁻¹): 3328, 2962, 2872, 1720, 1698, 1660, 1539, 1494, 1461, 1395, 1371, 1341, 1257, 1197, 1170, 1092, 1053, 765, 750

High Resolution FAB-MS (m/e, (C₃₁ H₄₆ N₄ O₈ +H)⁺): Calcd: 603.3394 Found: 603.3412

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.71 (3H, t, J=7.7 Hz), 0.88 (9H, s), 1.00-1.98 (8H, m), 1.31 (9H, s), 2.90 (1H, dd, J=10.5 Hz, 14.8 Hz), 3.11 (1H, dd, J=3.9 Hz, 14.8 Hz), 3.60-3.85 (1H, m), 3.94 (3H, s), 4.35-4.68 (2H, m), 6.73 (1H, d, J=8.3 Hz), 7.24 (1H, t, J=7.5 Hz), 7.31 (1H, t, J=7.5 Hz), 7.52 (1H, s), 7.72 (1H, d, J=7.5 Hz), 8.03 (1H, d, J=7.5 Hz), 8.12 (1H, d, J=7.4 Hz), 8.23 (1H, d, J=7.6 Hz)

EXAMPLE 16 Synthesis of Compound 16 (1) Preparation of Boc-DNal-DNle-OBzl

Boc-DNal-DNle-OBzl was prepared using Boc-DNal-OH instead of Boc-DTrp-OH in the same manner described in Example 14-(1).

FAB-MS (m/e, (C₃₁ H₃₈ N₂ O₅ +H)⁺): 519

(2) Preparation of H-DNal-DNle-OBzl

To a solution of Boc-DNal-DNle-OBzl (233 mg) in dichloromethane (2 ml) was added TFA (5 ml) and the mixture was stirred at room temperature for 13 h. The mixture was concentrated in vacuo. The residue was dissolved in dichloromethane, washed with sat. aq. NaHCO₃, water and brine successively, dried over MgSO₄ and evaporated in vacuo to give the product (185 mg).

FAB-MS (m/e, (C₂₆ H₃₀ N₂ O₃ +H)⁺): 419

(3) Preparation of Compound 16

To a solution of H-DNal-DNle-OBzl (180 mg, prepared in (2)) in dichloromethane (5 ml) were added Boc-Leu-OH.H₂ O (180 mg), HOBT.H₂ O (70 mg) and EDCI.HCl (99 mg) successively under ice cooling. After being stirred at room temperature for 14 h, the mixture was diluted with ethyl acetate, washed with sat. aq. NaHCO₃, 10% aq. citric acid, water and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by dry column flash chromatography (Merck, Kieselgel 60) with ethyl acetate/hexane=1/2 for elution to give Boc-Leu-DNal-DNle-OBzl (239 mg). A solution of the tripeptide derivative (87 mg) in 95% ethanol (10 ml) was hydrogenated over 10% Pd/C (21 mg) at an atmospheric pressure of hydrogen for 1 h. After removal of the catalyst by filtration, the filtrate was concentrated in vacuo to give Compound 16 (74 mg).

m.p.: 88°-90° C.

IR (KBr, cm⁻¹): 3304, 3070, 2962, 2872, 1725, 1698, 1656, 1536, 1461, 1398, 1371, 1251, 1167, 777

High Resolution FAB-MS (m/e, (C₃₀ H₄₃ N₃ O₆ +H)⁺): Calcd: 542.3230 Found: 542.3223

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.77-0.97 (9H, m), 1.12-1.89 (9H, m), 1.39+1.45 (9H, s×2), 3.48-3.66 (2H, m), 3.92-3.99 (1H, m), 4.33-4.40 (1H, m), 4.82-4.90 (1H, m), 5.07 (1H, brs), 6.81 (1H, brd, J=5.4 Hz), 6.85 (1H, brs), 7.32-7.38 (2H, m), 7.46 (1H, dd, J=8.0 Hz, 7.0 Hz), 7.53 (1H, dd, J=8.0 Hz, 7.0 Hz), 7.69-7.75 (1H, m), 7.82 (1H, d, J=8.0 Hz), 8.16 (1H, d, J=8.0 Hz)

EXAMPLE 17 Synthesis of Compound 17

Compound 17 was prepared using DLTrp(Me) instead of DNal in the same manner described in Example 16.

m.p.: 91°-98° C.

IR (KBr, cm⁻¹): 3322, 2962, 1653, 1530, 1476, 1371, 1251, 1167, 738

High Resolution FAB-MS (m/e, (C₂₉ H₄₄ N₄ O₆ +H)⁺): Calcd: 545.3339 Found: 545.3311

¹ H-NMR (300 MHz, DMSO-d₆, 70° C., δ ppm): 0.75 (3H, d, J=6.3 Hz), 0.78-0.89 (6H, m), 1.09-1.72 (9H, m), 1.34+1.36 (9H, s×2), 2.81-3.10 (2H, m), 3.69+3.70 (3H, s×2), 3.88-3.94 (1H, m), 4.10-4.22 (1H, m), 4.55-4.61 (1H, m), 6.45+6.60 (1H, brs×2), 6.98 (1H, t, J=8.1 Hz), 7.02+7.05 (1H, s×2), 7.10 (1H, t, J=8.1 Hz), 7.32 (1H, d, J=8.1 Hz), 7.53-7.78 (2H, m), 7.54+7.57 (1H, d×2, J=8.1 Hz)

EXAMPLE 18 Synthesis of Compound 18 (1) Preparation of H-DBal-DNle-O^(t) Bu

To a solution of Boc-DBal-OH (80 mg) in dichloromethane (10 ml) were added H-DNle-O^(t) Bu (67 mg), HOBT.H₂ O (41 mg) and EDCI.HCl (58 mg) successively at room temperature. After being stirred at room temperature for 6 h, the mixture was diluted with dichloromethane, washed with sat. aq NaHCO₃, 10% aq. citric acid, water and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel flash chromatography (Merck, Kieselgel 60) with chloroform for elution to give an oily product (123 mg), which was dissolved in formic acid. The mixture was stirred at room temperature for 2 h. The mixture was diluted with ethyl acetate, washed with sat. aq. NaHCO₃ and brine, dried over MgSO₄ and evaporated in vacuo to give H-DBal-DNle-O^(t) Bu (97 mg).

FAB-MS (m/e, (C₂₁ H₃₀ N₂ O₃ S+H)⁺): 391

(2) Preparation of (2-chlorophenyl)carbamoyl-Leu-OH

(2-Chlorophenyl)carbamoyl-Leu-OH was prepared using H-Leu-OBzl.TsOH as a starting material in the same manner described in Example 4.

FAB-MS (m/e, (C₁₃ H₁₇ ClN₂ O₃ +H)⁺): 285

(3) Preparation of Compound 18

To a solution of H-DBal-DNle-O^(t) Bu (98 mg, prepared in (1)) in DMF (10 ml) were added (2-chlorophenyl)carbamoyl-Leu-OH (85 mg, prepared in (2)), HOBT.H₂ O (46 mg) and EDCI.HCl (62 mg) successively under ice cooling. After being stirred at room temperature for 11 h, the reaction mixture was concentrated under reduced pressure. The residue was dissolved in chloroform and the solution was washed with sat. aq. NaHCO₃, 10% aq.citric acid and brine successively, dried over MgSO₄ and evaporated to give corresponding tripeptide derivative (148 mg). The tripeptide (102 mg) was dissolved in TFA (2 ml). The solution was stirred at room temperature for 2 h and evaporated in vacuo. The residue was purified by reprecipitation from methanol and water to give Compound 18 (81 mg).

m.p.: 182°-183° C.

IR (KBr, cm⁻¹): 3304, 3076, 2962, 1716, 1644, 1590, 1551, 1443, 750, 729

High Resolution FAB-MS (m/e, (C₃₀ H₃₇ ClN₄ O₅ S+H)⁺): Calcd: 601.2252 Found: 601.2255

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.77-0.82 (9H, m), 0.88-1.65 (9H, m), 3.32 (1H, dd, J=7.8 Hz, 14.5 Hz), 3.55 (1H, dd, J=5.5 Hz, 14.5 Hz), 4.06-4.15 (2H, m), 4.72-4.80 (1H, m), 6.80 (1H, brs), 6.88-6.97 (2H, m), 7.10-7.42 (6H, m), 7.56 (1H, brs), 7.78-7.88 (2H, m), 7.94-8.00 (1H, m)

EXAMPLE 19 Synthesis of Compound 19

Compound 19 was prepared using Boc-DLPhe(3-COOEt)-OH as a starting material in the same manner described in Example 18.

IR (KBr, cm⁻¹): 3322, 2962, 1725, 1647, 1542, 1287, 1203, 750

High Resolution FAB-MS (m/e, (C₃₁ H₄₁ ClN₄ O₇ +H)⁺): Calcd: 617.2742 Found: 617.2720

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.69 (3H, t, J=6.6 Hz), 0.79-0.88 (6H, m), 1.00-1.80 (9H, m), 1.30+1.33 (3H, t×2, J=7.0 Hz, J=7.0 Hz), 2.78+2.89 (1H, dd×2, J=11.7 Hz, 13.5 Hz, J=9.0 Hz, 13.5 Hz), 3.07+3.18 (1H, dd×2, J=5.5 Hz, 13.5 Hz, J=3.2 Hz, 13.5 Hz), 4.11-4.22 (2H, m), 4.28+4.29 (2H, q×2, J=7.0 Hz, J=7.0 Hz), 4.56-4.68 (1H, m), 6.90-6.97 (1H, m), 7.16-7.24 (2H, m), 7.31-7.41 (2H, m), 7.51+7.58 (1H, d×2, J=7.8 Hz, J=7.8 Hz), 7.75+7.79 (1H, d×2, J=7.8 Hz, J=7.8 Hz), 7.86+7.94 (1H, s×2), 8.06-8.24 (3H, m), 8.19+8.52 (1H, d×2, J=9.0 Hz, J=9.0 Hz)

EXAMPLE 20 Synthesis of Compound 20

Compound 20 was prepared using Boc-DLPhe(3-COOMe)-OH as a starting material in the same manner described in Example 18.

IR (KBr, cm⁻¹): 3322, 2962, 1728, 1647, 1545, 1446, 1290, 1209, 750

High Resolution FAB-MS (m/e, (C₃₀ H₃₉ ClN₄ O₇ +H)⁺): Calcd: 603.2585 Found: 603.2598

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.69 (3H, t, J=6.9 Hz), 0.80-0.93 (6H, m), 1.00-1.80 (9H, m), 2.78+2.89 (1H, dd×2, J=11.7 Hz, 13.5 Hz, J=9.0 Hz, 13.5 Hz), 3.07+3.18 (1H, dd×2, J=5.5 Hz, 13.5 Hz, J=3.2 Hz, 13.5 Hz), 3.81+3.84 (3H, s×2), 4.10-4.22 (2H, m), 4.57-4.68 (1H, m), 6.90-6.97 (1H, m), 7.16-7.24 (2H, m), 7.31-7.41 (2H, m), 7.51+7.58 (1H, d×2, J=7.8 Hz, J=7.8 Hz), 7.75+7.79 (1H, d×2, J=7.8 Hz, J=7.8 Hz), 7.87+7.95 (1H, s×2), 8.08-8.26 (3H, m), 8.22+8.52 (1H, d×2, J=8.8 Hz, J=8.8 Hz)

EXAMPLE 21 Synthesis of Compound 21 (1) Preparation of H-DTrp(COOMe)-DNle-O^(t) Bu.HCl

To a suspension of H-DNle-O^(t) Bu.HCl (603 mg) in dichloromethane (10 ml) were added NMM (297 μl), Boc-DTrp-OH (903 mg), HOBT.H₂ O (413 mg) and EDCI.HCl (569 mg) successively under ice cooling. The mixture was stirred at the same temperature for 2 h and at room temperature for 1 h. The reaction mixture was diluted with ethyl acetate, washed with 10% aq. citric acid, sat. aq. NaHCO₃, water and brine successively, dried over MgSO₄ and evaporated in vacuo to give Boc-DTrp-DNle-O^(t) Bu (1.22 g). To a solution of the dipeptide derivative in dichloromethane (12 ml) were added methyl chloroformate (1 ml), pulverized NaOH (103 mg) and TBAHS (20 mg). After being stirred of the mixture at room temperature for 30 min, pulverized NaOH (103 mg) was added. This procedure was repeated twice more. The reaction mixture was diluted with dichloromethane, washed with sat. aq. NaHCO₃, 10% aq. citric acid, water and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was recrystallized from ethyl acetate and hexane to give Boc-DTrp(COOMe)-DNle-O^(t) Bu (1.15 g). The dipeptide derivative (1.03 g) was dissolved in TFA (10 ml) and the solution was stirred under ice cooling for 10 min. After evaporation of the reaction mixture, the residue was dissolved in ethyl acetate. The solution was washed with sat. aq NaHCO₃, water and brine successively, dried over MgSO₄ and concentrated under reduced pressure to give H-DTrp(COOMe)-DNle-O^(t) Bu as a free base. To a solution of the free base (750 mg) in methanol was added 3.78N - hydrogen chloride/1,4-dioxane (0.47 ml) under ice cooling. The solution was evaporated in vacuo to give H-DTrp(COOMe)-DNle-O^(t) Bu.HCl (810 mg).

FAB-MS (m/e, (C₂₃ H₃₃ N₃ O₅ +H)⁺): 432

(2) Preparation of H-Leu-DTrp(COOMe)-DNle-O^(t) Bu

To a solution of H-DTrp(COOMe)-DNle-O^(t) Bu.HCl (60 mg, prepared in (1)) in DMF (2 ml) were added Z-Leu-OH (45 mg), HOBT.H₂ O (33 mg) and EDCI-HCl (41 mg) under ice cooling. After being stirred at the same temperature for 1 h, the mixture was diluted with ethyl acetate, washed with 10% aq. citric acid, sat. aq NaHCO₃ and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel flash chromatography (Merck, Kieselgel 60) with ethyl acetate/hexane=1/2 for elution to give an oily product (72 mg), which was dissolved in methanol (3 ml). The solution was hydrogenated over 10% Pd/C at an atmospheric pressure of hydrogen for 1 h. After removal of the catalyst by filtration, the filtrate was evaporated in vacuo to give H-Leu-DTrp(COOMe)-DNle-O^(t) Bu (48 mg).

(3) Preparation of Compound 21

To a solution of H-Leu-DTrp(COOMe)-DNle-O^(t) Bu (15 mg, prepared in (2)) in chloroform (1 ml) was added 2,6-dichlorophenylisocyanate (5.6 mg) at 0°-5° C. under argon atmosphere. The mixture was stirred at the same temperature for 1.5 h, and diluted with chloroform. The solution was washed with 1N-hydrochloric acid, sat. aq. NaHCO₃ and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol=30/1 for development to give an oily product (6.7 mg), which was dissolved in TFA (1 ml). After being stirred at room temperature for 1 h, the mixture was concentrated under reduced pressure. The residue was triturated with water to give Compound 21 (4.3 mg).

m.p.: 211°-212° C.

IR (KBr, cm⁻¹): 3310, 2962, 1740, 1647, 1545, 1461, 1386, 1260, 1092, 765

High Resolution FAB-MS (m/e, (C₃₂ H₃₉ C₁₂ N₅ O₇ +H)⁺): Calcd: 676.2305 Found: 676.2297

¹ H-NMR (300 MHz, Acetone-d₆, δ ppm): 0.78 (3H, d, J=6.1 Hz), 0.79 (3H, d, J=6.1 Hz), 0.80 (3H, t, J=8.4 Hz), 1.10-1.76 (9H, m), 3.08 (1H, dd, J=9.6 Hz, 15.1 Hz), 3.37 (1H, dd, J=4.7 Hz, 15.1 Hz), 4.00 (3H, s), 4.14-4.31 (2H, m), 4.77-4.91 (1H, m), 6.32 (1H, d, J=7.1 Hz), 7.23 (1H, t, J=7.8 Hz), 7.28 (1H, t, J=7.7 Hz), 7.33 (1H, t, J=7.7 Hz), 7.40 (2H, d, J=7.8 Hz), 7.58 (1H, s), 7.60 (1H, s), 7.66 (1H, d, J=7.6 Hz), 7.70 (1H, d, J=7.3 Hz), 7.70 (1H, d, J=7.7 Hz), 8.14 (1H, d, J=7.7 Hz)

Each Compound 22-24 in the following Examples 22-24 was prepared using corresponding isocyanate in the same manner described in Example 21-(3).

EXAMPLE 22 Compound 22

m.p.: 208°-209° C.

IR (KBr, cm⁻¹): 3352, 2962, 2872, 1737, 1647, 1551, 1461, 1389, 1260, 1095, 750

High Resolution FAB-MS (m/e, (C₃₂ H₄₀ FN₅ O₇ +H)⁺): Calcd: 626.2990 Found: 626.2984

¹ H-NMR (300 MHz, Acetone-d₆, δ ppm): 0.78 (3H, d, J=6.3 Hz), 0.80 (3H, d, J=6.3 Hz), 0.86 (3H, t, J=6.9 Hz), 1.20-1.50 (7H, m), 1.65-1.90 (2H, m), 3.12 (1H, dd, J=9.6 Hz, 15.0 Hz), 3.38 (1H, dd, J=4.7 Hz, 15.0 Hz), 4.01 (3H, s), 4.19-4.29 (1H, m), 4.34-4.46 (1H, m), 4.79-4.90 (1H, m), 6.46 (1H, d, J=7.1 Hz), 6.88-6.99 (1H, m), 7.00-7.14 (2H, m), 7.25 (1H, t, J=7.8 Hz), 7.32 (1H, t, J=7.8 Hz), 7.61 (1H, s), 7.67 (1H, d, J=8.0 Hz), 7.70 (1H, d, J=7.8 Hz), 7.81 (1H, d, J=8.2 Hz), 7.91 (1H, d, J=2.1 Hz), 8.14 (1H, d, J=7.8 Hz), 8.17-8.27 (1H, m)

EXAMPLE 23 Compound 23

m.p.: 212°-224° C.

IR (KBr, cm⁻¹): 3322, 3088, 2962, 2872, 1740, 1647, 1554, 1461, 1389, 1326, 1260, 1122, 762

High Resolution FAB-MS (m/e, (C₃₃ H₄₀ F₃ N₅ O₇ +H)⁺): Calcd: 676.2958 Found: 676.2957

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.64 (3H, d, J=6.1 Hz), 0.65 (3H, d, J=6.1 Hz), 0.81 (3H, t, J=7.1 Hz), 0.78-1.82 (9H, m), 2.88 (1H, dd, J=11.2 Hz, 14.7 Hz), 3.10-3.25 (1H, m), 3.95 (3H, s), 4.10-4.28 (2H, m), 4.62-4.76 (1H, m), 7.10-7.24 (2H, m), 7.26 (1H, t, J=7.6 Hz), 7.33 (1H, t, J=7.6 Hz), 7.54 (1H, s), 7.43-7.63 (2H, m), 7.76 (1H, d, J=7.6 Hz), 7.88 (1H, d, J=7.9 Hz), 7.88 (1H, s), 8.05 (1H, d, J=7.6 Hz), 8.22 (1H, d, J=7.9 Hz), 8.49 (1H, d, J=8.4 Hz)

EXAMPLE 24 Compound 24

m.p.: 186°-188° C.

IR (KBr, cm⁻¹): 3346, 2962, 1740, 1653, 1506, 1458, 1386, 1344, 1260, 1092, 741

High Resolution FAB-MS (m/e, (C₃₂ H₄₀ N₆ O₉ +H)⁺): Calcd: 653.2935 Found: 653.2939

¹ H-NMR (300 MHz, Acetone-d₆, δ ppm): 0.79 (3H, d, J=6.4 Hz), 0.81 (3H, d, J=6.4 Hz), 0.83 (3H, t, J=7.2 Hz), 1.14-1.50 (7H, m), 1.65-1.90 (2H, m), 3.11 (1H, dd, J=9.6 Hz, 14.8 Hz), 3.39 (1H, dd, J=4.2 Hz, 14.8 Hz), 4.01 (3H, s), 4.17-4.29 (1H, m), 4.37-4.49 (1H, m), 4.79-4.90 (1H, m), 7.12 (1H, dt, J=1.4 Hz, 7.2 Hz), 7.25 (1H, t, J=7.6 Hz), 7.31 (1H, t, J=7.6 Hz), 7.20-7.37 (1H, m), 7.55-7.67 (2H, m), 7.60 (1H, s), 7.69 (1H, d, J=7.6 Hz), 7.78 (1H, d, J=9.1 Hz), 8.12 (1H, d, J=7.6 Hz), 8.13 (1H, d, J=8.2 Hz), 8.54 (1H, dd, J=1.4 Hz, 7.2 Hz), 9.56 (1H, s)

EXAMPLE 25 Synthesis of Compound 25

A solution of Compound 24 (30 mg, obtained in Example 24) in 95% ethanol (3 ml) was hydrogenated over 10% Pd/C (20 mg) at an atmospheric pressure of hydrogen for 1.5 h. After removal of the catalyst by filtration, the filtrate was evaporated in vacuo to give Compound 25 (26 mg).

m.p.: 188°-190° C.

IR (KBr, cm⁻¹): 3370, 2962, 1740, 1650, 1551, 1461, 1386, 1260, 747

High Resolution FAB-MS (m/e, (C₃₂ H₄₂ N₆ O₇ +H)⁺): Calcd: 623.3193 Found: 623.3157

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.64 (3H, d, J=6.5 Hz), 0.66 (3H, d, J=6.5 Hz), 0.83 (3H, t, J=7.0 Hz), 0.78-1.40 (7H, m), 1.56-1.78 (2H, m), 2.88 (1H, dd, J=11.8 Hz, 14.9 Hz), 3.15 (1H, dd, J=2.8 Hz, 14.9 Hz), 3.95 (3H, s), 4.09-4.21 (2H, m), 4.60-4.73 (1H, m), 6.28 (1H, d, J=8.1 Hz), 6.47 (1H, dt, J=1.7 Hz, 7.7 Hz), 6.64 (1H, dd, J=1.7 Hz, 7.7 Hz), 6.74 (1H, dt, J=1.7 Hz, 7.7 Hz), 7.26 (1H, t, J=7.6 Hz), 7.27 (1H, dd, J=1.7 Hz, 7.7 Hz), 7.33 (1H, t, J=7.6 Hz), 7.54 (1H, s), 7.59 (1H, s), 7.76 (1H, d, J=7.6 Hz), 8.05 (1H, d, J=7.6 Hz), 8.23 (1H, d, J=7.3 Hz), 8.46 (1H, d, J=8.6 Hz)

EXAMPLE 26 Synthesis of Compound 26

To a solution of Compound 25 (15 mg, obtained in Example 25) were added TEA (21 μl) and formic pivalic anhydride (15 μl) at 0°-5° C. under argon atmosphere. The mixture was stirred at the same temperature for 5 h. Water was added to the reaction mixture. The mixture was acidified with 1N-hydrochloric acid and extracted with ethyl acetate. The ethyl acetate extract was dried over anhydrous sodium sulfate and evaporated in vacuo. The residue was purified by preparative TLC (3M, Empore Silica Sheet) with chloroform/methanol/acetic acid=20/1/1 for development and the product was triturated with methanol and water to give Compound 26 (11 mg).

m.p.: 174°-178° C.

IR (KBr, cm⁻¹): 3310, 2962, 1743, 1665, 1554, 1461, 1389, 1260, 1092, 747

High Resolution FAB-MS (m/e, (C₃₃ H₄₂ N₆ O₈ +H)⁺): Calcd: 651.3143 Found: 651.3134

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.67 (3H, d, J=6.1 Hz), 0-74 (3H, d, J=6.1 Hz), 0.70 (3H, t, J=7.2 Hz), 1.00-2.00 (9H, m), 2.81-2.99 (1H, m), 3.07-3.20 (1H, m), 3.87 (3H, s), 4.20-4.48 (2H, m), 4-60-4.90 (1H, m), 6.87 (1H, dt, J=1.4 Hz, 7.1 Hz), 7.00 (1H, dt, J=1.4 Hz, 7.1 Hz), 7.05-7.34 (2H, m), 7.16 (1H, t, J=7.7 Hz), 7.28 (1H, t, J=7.7 Hz), 7.48 (1H, s), 7.45-7.59 (2H, m), 7.61 (1H, d, J=7.7 Hz), 7.78 (1H, brs), 8.03 (1H, d, J=7.7 Hz), 8.47 (1H, brs), 8.78 (1H, d, J=8.3 Hz), 11.77 (1H, brs)

EXAMPLE 27 Synthesis of Compound 27 (1) Preparation of PhOCO-Leu-DTrp(COOMe)-DNle-O^(t) Bu

To a solution of H-Leu-DTrp(COOMe)-DNle-O^(t) Bu (320 mg, prepared in Example 21-(2)) in pyridine (2.3 ml) was added phenyl chloroformate at 0°-5° C. under argon atmosphere. The mixture was stirred at the same temperature for 1.5 h and concentrated in vacuo. The residue was dissolved in ethyl acetate and the solution was washed with 10% aq. citric acid, sat. aq. NaHCO₃ and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel flash chromatography (Merck, Kieselgel 60) with ethyl acetate/hexane=2/1 for elution to give the product (337 mg).

FAB-MS (m/e, (C₃₆ H₄₈ N₄ O₈ +H)⁺): 665

(2) Preparation of Compound 27

A solution of PhOCO-Leu-DTrp(COOMe)-DNle-O^(t) Bu (10 mg, prepared in (1)) in TFA (1 ml) was stirred at room temperature for 1 h. The mixture was evaporated in vacuo and the residue was triturated with water to give Compound 27 (5.8 mg).

m.p.: 198°-199° C.

IR (KBr, cm⁻¹): 3316, 2962, 2872, 1740, 1653, 1536, 1461, 1386, 1260, 1209, 1092, 762

High Resolution FAB-MS (m/e, (C₃₂ H₄₀ N₄ O₈ +H)⁺): Calcd: 609.2924 Found: 609.2899

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.68 (3H, d, J=6.3 Hz), 0.69 (3H, d, J=6.3 Hz), 0.81 (3H, t, J=7.1 Hz), 1.00-1.75 (9H, m), 2.88 (1H, dd, J=11.0 Hz, 14.4 Hz), 3.14 (1H, dd, J=5.6 Hz, 14.4 Hz), 3.94 (3H, s), 3.96-4.20 (2H, m), 4.63-4.75 (1H, m), 7.01 (2H, dd, J=1.3 Hz, 8.3 Hz), 7.16 (1H, dt, J=1.3 Hz, 8.3 Hz), 7.25 (1H, t, J=7.7 Hz), 7.27-7.37 (3H, m), 7.52 (1H, s), 7.75 (1H, d, J=7.7 Hz), 7.83 (1H, d, J=7.8 Hz), 8.05 (1H, d, J=7.8 Hz), 8.14 (1H, d, J=7.7 Hz), 8.41 (1H, d, J=8.8 Hz)

EXAMPLE 28 Synthesis of Compound 28

To a solution of PhOCO-Leu-DTrp(COOMe)-DNle-O^(t) Bu (33 mg, prepared in Example 27-(1)) in chloroform were added hexamethyleneimine (56 μl) and TEA (100 μl) at room temperature under argon atmosphere. The mixture was stirred at 55° C. for 2 h and cooled to room temperature. The mixture was diluted with ethyl acetate, washed with 1N-hydrochloric acid, sat. aq. NaHCO₃ and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with ethyl acetate/hexane=1/1 for development to give an oily product (28 mg), which was dissolved in TFA (1 ml). After being stirred at room temperature for 1 h, the mixture was evaporated in vacuo. The residue was triturated with water to give Compound 28 (22 mg).

m.p.: 94°-97° C.

IR (KBr, cm⁻¹): 3352, 2938, 1743, 1635, 1536, 1461, 1386, 1260, 1221, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₂ H₄₇ N₅ O₇ +H)⁺): Calcd: 614.3554 Found: 614.3532

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.79 (3H, d, J=6.1 Hz), 0.80 (3H, d, J=6.1 Hz), 0.83 (3H, t, J=6.8 Hz), 1.10-1.93 (17H, m), 3.10-3.45 (6H, m), 3.88-3.98 (1H, m), 4.02 (3H, s), 4.35-4.45 (1H, m), 4.77-4.85 (1H, m), 5.21 (1H, brs), 6.74 (1H, d, J=8.0 Hz), 7.25 (1H, t, J=7.6 Hz), 7.34 (1H, t, J=7.6 Hz), 7.49 (1H, s), 7.58 (1H, d, J=7.6 Hz), 7.66 (1H, d, J=8.4 Hz), 8.16 (1H, d, J=7.6 Hz)

Each Compound 29-32 in the following Examples 29-32 was prepared using each corresponding amine as a starting material in the same manner described in Example 28.

EXAMPLE 29 Compound 29

m.p.: 106°-110° C.

IR (KBr, cm⁻¹): 3328, 2962, 1743, 1635, 1539, 1461, 1386, 1257, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₀ H₄₃ N₅ O₇ S+H)⁺): Calcd: 618.2961 Found: 618.2987

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.80 (3H, d, J=5.5 Hz), 0.81 (3H, d, J=5.5 Hz), 0.83 (3H, t, J=7.1 Hz), 1.08-1.90 (9H, m), 2.49-2.64 (4H, m), 3.24 (1H, dd, J=7.3 Hz, 15.1 Hz), 3.31 (1H, dd, J=6.1 Hz, 15.1 Hz), 3.55-3.73 (4H, m), 3.88-3.98 (1H, m), 4.03 (3H, s), 4.27-4.37 (1H, m), 4.70-4.80 (1H, m), 5.73 (1H, brs), 6.68 (1H, d, J=8.1 Hz), 7.26 (1H, t, J=7.8 Hz), 7.35 (1H, t, J=7.8 Hz), 7.49 (1H, s), 7.50 (1H, d, J=6.6 Hz), 7.57 (1H, d, J=7.8 Hz), 8.16 (1H, d, J=7.8 Hz)

EXAMPLE 30 Compound 30

m.p.: 104°-109° C.

IR (KBr, cm⁻¹): 3322, 2962, 1743, 1644, 1536, 1461, 1386, 1260, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₀ H₄₃ N₅ O₇ +H)⁺): Calcd: 586.3241 Found: 586.3264

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.79 (3H, d, J=6.0 Hz), 0.81 (3H, d, J=6.0 Hz), 0.83 (3H, t, J=7.1 Hz), 1.10-1.98 (13H, m), 3.13-3.40 (6H, m), 3.87-3.98 (1H, m), 4.02 (3H, s), 4.39-4.48 (1H, m), 4.78-4.85 (1H, m), 5.14 (1H, d, J=5.9 Hz), 6.69 (1H, d, J=8.0 Hz), 7.25 (1H, t, J=7.4 Hz), 7.34 (1H, t, J=7.4 Hz), 7.49 (1H, s), 7.59 (1H, d, J=7.4 Hz), 7.74 (1H, d, J=7.9 Hz), 8.16 (1H, d, J=7.4 Hz)

EXAMPLE 31 Compound 31

m.p.: 96°-101° C.

IR (KBr, cm⁻¹): 3322, 2956, 2866, 1743, 1638, 1539, 1461, 1386, 1260, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₁ H₄₅ N₅ O₇ +H)⁺): Calcd: 600.3397 Found: 600.3385

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.77 (3H, d, J=6.3 Hz), 0.79 (3H, d, J=6.3 Hz), 0.83 (3H, t, J=7.1 Hz), 1.10-1.92 (15H, m), 3.15-3.37 (6H, m), 3.86-3.98 (1H, m), 4.02 (3H, s), 4.31-4.40 (1H, m), 4.73-4.80 (1H, m), 5.52 (1H, brs), 6.80 (1H, d, J=6.4 Hz), 7.25 (1H, t, J=7.6 Hz), 7.34 (1H, t, J=7.6 Hz), 7.50 (1H, s) 7.58 (1H, d, J=7.6 Hz), 7.62 (1H, d, J=7.2 Hz), 8.16 (1H, d, J=7.6 Hz)

EXAMPLE 32 Compound 32

m.p.: 104°-108° C.

IR (KBr, cm⁻¹): 3328, 2962, 1743, 1647, 1539, 1461, 1386, 1260, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₂₉ H₄₁ N₅ O₇ S+H)⁺): Calcd: 604.2805 Found: 604.2799

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.75-0.86 (9H, m), 1.05-1.92 (9H, m), 2.90-3.00 (2H, m), 3.28 (2H, d, J=7.4 Hz), 3.39-3.48 (1H, m), 3.62-3.70 (1H, m), 3.85-3.95 (1H, m), 4.03 (3H, s), 4.17 (1H, d, J=9.1 Hz), 4.43 (1H, d, J=9.1 Hz), 4.48-4.56 (1H, m), 4.73-4.82 (1H, m), 5.93 (1H, brs), 6.57 (1H, d, J=8.5 Hz), 7.26 (1H, t, J=7.8 Hz), 7.35 (1H, t, J=7.8 Hz), 7.49 (1H, s), 7.58 (1H, d, J=7.8 Hz), 7.59 (1H, d, J=11.9 Hz), 8.16 (1H, d, J=7.8 Hz)

EXAMPLE 33 Synthesis of Compound 33 (1) Preparation of PhOCO-Leu-OBzl

To a solution of H-Leu-OBzl.TsOH (1.01 g) in pyridine (9 ml) was added phenyl chloroformate (386 μl) at 0°-5° C. under argon atmosphere. The mixture was stirred at the same temperature for 2 h and concentrated in vacuo. The residue was dissolved in ethyl acetate and the solution was washed with 1N-hydrochloric acid, water and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel chromatography (Merck, Kieselgel 60) with ethyl acetate/hexane=1/10 for elution to give the product (828 mg).

FAB-MS (m/e, (C₂₀ H₂₃ NO₄ +H)⁺): 342

(2) Preparation of ^(i) Pr₂ NCO-Leu-OBzl

To a solution of PhOCO-Leu-OBzl (70 mg, prepared in (1)) in chloroform (2 ml) were added diisopropylamine (575 μl) and TEA (286 μl) at room temperature under argon atmosphere. The mixture was stirred at 55° C. for 17 h and cooled to room temperature. The mixture was diluted with ethyl acetate, washed with 1N-hydrochloric acid, sat. aq. NaHCO₃ and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with ethyl acetate/hexane=1/4 for development to give the product (32 mg).

FAB-MS (m/e, (C₂₀ H₃₂ N₂ O₃ +H)⁺): 349

(3) Preparation of Compound 33

A mixture of ^(i) Pr₂ NCO-Leu-OBzl (32 mg, obtained in (2)) and 10% Pd/C (10 mg) in methanol (1 ml) was stirred at room temperature under an atmospheric pressure of hydrogen for 16 h. The catalyst was filtered off and the filtrate was concentrated under reduced pressure. The residue was dissolved in dichloromethane (1.5 ml). To the solution were added H-DTrp(COOMe)-DNle-O^(t) Bu.HCl (40 mg, prepared in Example 21-(1)), NMM (10 μl), HOBT.H₂ O (13 mg) and EDCI.HCl (18 mg) under ice cooling.

After being stirred at room temperature for 1.5 h, the mixture was diluted with ethyl acetate, washed with sat. aq. NaHCO₃, 10% aq. citric acid, water and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with ethyl acetate/hexane=1/1 for development to give the product (52 mg), which was dissolved in TFA (1 ml). After being stirred at room temperature for 1 h, the mixture was evaporated in vacuo. The residue was triturated with water to give Compound 33 (18 mg).

m.p.: 94°-96° C.

IR (KBr, cm⁻¹): 3322, 2962, 2872, 1743, 1650, 1524, 1461, 1386, 1341, 1311, 1260, 1221, 1149, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₂ H₄₉ O₇ N₅ +H)⁺): Calcd: 616,3718 Found: 616,3699

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.66 (3H, d, J=6.0 Hz), 0.67 (3H, d, J=6.0 Hz), 0.85 (3H, t, J=7.0 Hz), 1.08+1.10 (12H, d×2, J=6.8 Hz), 1.10-1.40 (7H, m), 1.15-1.30 (2H, m), 2.86 (1H, dd, J=11.0 Hz, 14.8 Hz), 3.18 (1H, dd, J=3.5 Hz, 14.8 Hz), 3.70 (2H, sept, J=6.8 Hz), 3.95 (3H, s), 3.95-4.07 (1H, m), 4.10-4.20 (1H, m), 4.60-4.70 (1H, m), 5.56 (1H, d, J=7.3 Hz), 7.25 (1H, t, J=7.6 Hz), 7.32 (1H, t, J=7.6 Hz), 7.49 (1H, s), 7.70 (1H, d, J=7.6 Hz), 8.04 (1H, d, J=7.6 Hz), 8.15 (1H, d, J=8.1 Hz), 8.18 (1H, d, J=9.3 Hz)

Each Compound 34 and 35 in the following Examples 34 and 35 was prepared using corresponding amine in the same manner described in Example 33-(2) and (3).

EXAMPLE 34 Compound 34

m.p.: 85°-94° C.

IR (KBr, cm⁻¹): 3328, 2962, 2872, 1743, 1638, 1533, 1461, 1383, 1344, 1311, 1260, 1224, 1200, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₂ H₄₇ N₅ O₇ +H)⁺): Calcd: 614.3554 Found: 614.3569

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.66 (3H, d, J=6.0 Hz), 0.68 (3H, d, J=6.0 Hz), 0.86 (3H, t, J=7.0 Hz), 1.06 (3H, d, J=6.1 Hz), 1.09 (3H, d, J=6.1 Hz), 1.10-1.40 (7H, m), 1.40-1.60 (2H, m), 1.65-1.78 (2H, m), 1.80-1.94 (2H, m), 2.86 (1H, dd, J=4.0 Hz, 10.7 Hz), 3.12-3.30 (1H, m), 3.78 (2H, sext, 6.1 Hz), 3.96 (3H, s), 4.08-4.20 (2H, m), 4.50-4.68 (1H, m), 5.65 (1H, d, J=6.8 Hz), 7.27 (1H, t, J=7.4 Hz), 7.32 (1H, t, J=7.4 Hz), 7.49 (1H, s), 7.68 (1H, d, J=7.4 Hz), 8.05 (1H, d, J=7.4 Hz), 8.20-8.31 (2H, m)

EXAMPLE 35 Compound 35

m.p.: 100°-110° C.

IR (KBr, cm⁻¹): 3376, 2962, 2866, 1743, 1632, 1539, 1461, 1386, 1341, 1311, 1260, 1188, 1152, 747

High Resolution FAB-MS (m/e, (C₃₂ H₄₇ N₅ O₇ +H)⁺): Calcd: 614,3554 Found: 614,3540

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.62-0.75 (6H, m), 0.86 (3H, t, J=7.0 Hz), 0.95+0.97 (3H, d×2, J=6.8 Hz), 1.03-1.58 (13H, m), 1.65-1.78 (2H, m), 2.77-2.91 (1H, m), 3.15-3.50 (2H, m), 3.63-3.77 (1H, m), 3.86-4.00 (1H, m), 4.01 (3H, s), 4.04-4.30 (2H, m), 4.53-4.64 (1H, m), 6.15-6.25 (1H, m), 7.25 (1H, t, J=7.3 Hz), 7.32 (1H, t, J=7.3 Hz), 7.47+7.48 (1H, s×2), 7.66+7.67 (1H, d×2, J=7.3 Hz), 8.05 (1H, d, J=7.3 Hz), 8.15-8.28 (2H, m)

EXAMPLE 36 Synthesis of Compound 36 (1) Preparation of (c-Pent)nPrNCO-Leu-OBzl

To a mixture of H-Leu-OBzl.TsOH (1.0 g) and CDI (469 mg) in chloroform (10 ml) was added TEA (0.43 ml) at room temperature and the mixture was stirred at the same temperature for 1 h. Cyclopentylpropylamine (0.47 ml) was added and the reaction mixture was stirred at room temperature for 6 h. The mixture was diluted with ethyl acetate, washed with 1N-hydrochloric acid and brine, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel chromatography (Merck, Kieselgel 60) with ethyl acetate/hexane=3/7 for elution to give the product (850 mg).

FAB-MS (m/e, (C₂₂ H₃₄ NO₃ +H)⁺): 375

(2) Preparation of Compound 36

Compound 36 was prepared using (c-Pent)nPrNCO-Leu-OBzl (prepared in (1)) as a starting material in the same manner described in Example 33-(3).

m.p.: 68°-73° C.

IR (KBr, cm⁻¹): 3382, 2962, 2872, 1743, 1632, 1533, 1461, 1386, 1344, 1311, 1260, 1227, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₄ H₅₁ N₅ O₇ +H)⁺): 642

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.81 (3H, d, J=5.8 Hz), 0.82 (3H, d, J=6.7 Hz), 0.83 (3H, t, J=6.7 Hz), 0.87 (3H, t, J=7.3 Hz), 1.12-1.95 (19H, m), 2.91 (1H, dt, J=7.9 Hz, 15.8 Hz), 3.00 (1H, dt, J=7.9 Hz, 15.8 Hz), 3.27 (1H, dd, J=4.5 Hz, 15.0 Hz), 3.33 (1H, dd, J=6.0 Hz, 15.0 Hz), 3.84-3.98 (1H, m), 4.02 (3H, s), 4.14 (1H, quint, J=7.9 Hz), 4.34 (1H, ddd, J=4.6 Hz, 6.4 Hz, 8.2 Hz), 4.75 (1H, d, J=6.4 Hz), 4.78-4.86 (1H, m), 6.60 (1H, d, J=7.9 Hz), 7.26 (1H, t, J=7.6 Hz), 7.35 (1H, t, J=7.6 Hz), 7.48 (1H, s), 7.59 (1H, d, J=7.6 Hz), 7.61 (1H, d, J=8.2 Hz), 8.16 (1H, d, J=7.6 Hz)

Each Compound 37-39 in the following Examples 37-39 was prepared using each corresponding amine as a starting material in the same manner described in Example 36.

EXAMPLE 37 Compound 37

m.p.: 98°-107° C.

IR (KBr, cm⁻¹): 3388, 2914, 2860, 1743, 1653, 1551, 1461, 1386, 1260, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₅ H₄₅ N₅ O₇ +H)⁺): Calcd: 648.3398 Found: 648.3346

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (3H, d, J=5.6 Hz), 0.69 (3H, d, J=5.6 Hz), 0.86 (3H, t, J=7.0 Hz), 1.07-1.45 (7H, m), 1.65-1.83 (2H, m), 2.60-2.80 (2H, m), 2.86 (1H, dd, J=11.0 Hz, 14.4 Hz, 3.15-3.30 (1H, m), 3.30-3.60 (2H, m), 3.94 (3H, s), 3.94-4.05 (1H, m), 4.06-4.20 (1H, m), 4.39 (1H, d, J=16.4 Hz), 4.50 (1H, d, J=16.4 Hz), 4.52-4.66 (1H, m), 6.44 (1H, d, J=7.1 Hz), 7.00-7.19 (4H, m), 7.23 (1H, t, J=7.5 Hz), 7.31 (1H, t, J=7.5 Hz), 7.49 (1H, s), 7.68 (1H, d, J=7.5 Hz), 8.04 (1H, d, J=7.5 Hz), 8.19 (1H, d, J=7.6 Hz), 8.30 (1H, d, J=8.7 Hz)

EXAMPLE 38 Compound 38

m.p.: 79°-82° C.

IR (KBr, cm⁻¹): 3316, 2692, 2872, 1743, 1629, 1533, 1461, 1386, 1341, 1311, 1260, 1227, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₅ H₅₃ N₅ O₇ +H)⁺): Calcd: 656.4024 Found: 656.4029

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.81 (3H, d, J=6.3 Hz), 0.82 (3H, d, J=6.3 Hz), 0.83 (3H, t, J=6.3 Hz), 0.91 (3H, t, J=7.4 Hz), 1.10-1.95 (21H, m), 2.93 (1H, dt, J=7.5 Hz, 15.0 Hz), 3.00 (1H, dt, J=7.5 Hz, 15.0 Hz), 3.27 (1H, dd, J=6.6 Hz, 15.0 Hz), 3.31 (1H, dd, J=6.0 Hz, 15.0 Hz), 3.91 (1H, q, J=6.7 Hz), 4.02 (3H, s), 4.14 (1H, quint, J=8.2 Hz), 4.34 (1H, ddd, J=5.4 Hz, 6.4 Hz, 8.7 Hz), 4.72 (1H, d, J=6.4 Hz), 4.82 (1H, ddd, J=6.0 Hz, 6.6 Hz, 7.6 Hz), 6.56 (1H, d, J=7.6 Hz), 7.26 (1H, t, J=7.6 Hz), 7.35 (1H, t, J=7.6 Hz), 7.48 (1H, s), 7.59 (1H, d, J=6.7 Hz), 7.64 (1H, d, J=7.6 Hz), 8.16 (1H, d, J=7.6 Hz)

EXAMPLE 39 Compound 39

m.p.: 95°-110° C.

IR (KBr, cm⁻¹): 3334, 2962, 2872, 1743, 1662, 1536, 1461, 1386, 1344, 1311, 1260, 1149, 1128, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₃ H₄₉ N₅ O₇ +H)⁺): Calcd: 628.3718 Found: 628.3699

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.66 (3H, d, J=6.0 Hz), 0.70 (3H, d, J=6.0 Hz), 0.86 (3H, t, J=7.1 Hz), 1.01 (3H, d, J=7.2 Hz), 1.04 (3H, d, J=7.2 Hz), 1.05-1.55 (11H, m), 1.60-1.80 (4H, m), 2.84 (1H, dd, J=11.5 Hz, 15.0 Hz), 3.15-3.25 (1H, m), 3.95 (3H, s), 4.01-4.18 (4H, m), 4.54-4.65 (1H, m), 6.04 (1H, d, J=6.9 Hz), 7.25 (1H, t, J=7.5 Hz), 7.32 (1H, t, J=7.5 Hz), 7.48 (1H, s), 7.67 (1H, d, J=7.5 Hz), 8.05 (1H, d, J=7.5 Hz), 8.20 (1H, d, J=7.6 Hz), 8.24 (1H, d, J=8.8 Hz)

Each Compound 40-43 in the following Examples 40-43 was prepared using each corresponding amino acid benzyl ester tosylate as a starting material in the same manner described in Example 39.

EXAMPLE 40 Compound 40

m.p.: 103°-107° C.

IR (KBr, cm⁻¹): 3376, 2956, 2872, 1743, 1656, 1530, 1461, 1386, 1341, 1260, 1227, 1137, 1092, 765, 747

FAB-MS (m/e, (C₃₄ H₅₁ N₅ O₇ +H)⁺): 642

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.82 (3H, t, J=7.3 Hz), 0.85 (9H, s), 1.14 (6H, d, J=7.1 Hz), 1.20-1.90 (14H, m), 3.26 (1H, dd, J=5.5 Hz, 14.6 Hz), 3.35 (1H, dd, J=6.3 Hz, 14.6 Hz), 3.85-3.95 (2H, m), 4.02 (3H, s), 4.09-4.21 (1H, m), 4.28 (1H, ddd, J=5.3 Hz, 6.2 Hz, 8.3 Hz), 4.76 (1H, ddd, J=5.5 Hz, 6.3 Hz, 8.3 Hz), 4.93 (1H, d, J=6.2 Hz), 6.48 (1H, d, J=8.3 Hz), 7.27 (1H, t, J=7.6 Hz), 7.35 (1H, t, J=7.6 Hz), 7.48 (1H, s), 7.58 (1H, d, J=7.6 Hz), 7.72 (1H, d, J=7.3 Hz), 8.16 (1H, d, J=7.6 Hz)

EXAMPLE 41 Compound 41

m.p.: 101°-104.5° C.

IR (KBr, cm⁻¹): 3286, 2944, 2872, 1743, 1653, 1560, 1530, 1461, 1386, 1341, 1311, 1260, 1143, 1092, 756

High Resolution FAB-MS (m/e, (C₃₆ H₄₇ N₅ O₇ +H)⁺): Calcd: 662.3554 Found: 662.3530

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.70-1.92 (12H, m), 0.77 (3H, t, J=7.4 Hz), 1.01 (3H, d, J=7.1 Hz), 1.04 (3H, d, J=7.1 Hz), 2.90 (1H, dd, J=5.1 Hz, 14.5 Hz), 2.94 (1H, dd, 6.5 Hz, 12.6 Hz), 3.06 (1H, dd, J=8.1 Hz, 12.6 Hz), 3.32 (1H, dd, J=5.1 Hz, 14.5 Hz), 3.74-3.93 (1H, m), 3.93-4.12 (2H, m), 4.03 (3H, s), 4.27 (1H, ddd, J=4.6 Hz, 6.5 Hz, 8.1 Hz), 4.69 (1H, dt, J=5.1 Hz, 7.6 Hz), 5.05 (1H, brs), 6.32 (1H, d, J=6.7 Hz), 7.06-7.45 (9H, m), 7.60 (1H, brs), 8.14 (1H, d, J=7.9 Hz)

EXAMPLE 42 Compound 42

m.p.: 102°-110° C.

IR (KBr, cm⁻¹): 3406, 2932, 2860, 1743, 1665, 1536, 1461, 1386, 1341, 1260, 1203, 1149, 1128, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₆ H₅₃ N₅ O₇ +H)⁺): Calcd: 668.4024 Found: 668.4004

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.70-1.92 (25H, m), 0.81 (3H, t, J=7.1 Hz), 1.14 (3H, d, J=7.0 Hz), 1.15 (3H, d, J=7.0 Hz), 3.23 (1H, dd, J=5.3 Hz, 15.1 Hz), 3.36 (1H, dd, J=7.0 Hz, 15.1 Hz), 3.85-4.20 (3H, m), 4.02 (3H, s), 4.22-4.38 (1H, m), 4.73-4.90 (1H, m), 5.02 (1H, brs), 6.63 (1H, d, J=6.2 Hz), 7.26 (1H, t, J=7.3 Hz), 7.35 (1H, t, J=7.3 Hz), 7.49 (1H, s), 7.59 (1H, d, J=7.3 Hz), 7.65 (1H, d, J=7.0 Hz), 8.16 (1H, d, J=7.3 Hz)

EXAMPLE 43 Compound 43

m.p.: 96°-104° C.

IR (KBr, cm⁻¹): 3328, 2962, 2872, 1743, 1656, 1530, 1461, 1386, 1341, 1311, 1260, 1227, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₂ H₄₇ N₅ O₇ +H)⁺): Calcd: 614.3554 Found: 614.3558

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.79 (3H, d, J=6.7 Hz), 0.82 (3H, t, J=7.0 Hz), 0.90 (3H, d, J=6.7 Hz), 1.00-1.40 (6H, m), 1.17 (3H, d, J=7.0 Hz), 1.18 (3H, d, J=7.0 Hz), 1.42-2.10 (7H, m), 3.26 (1H, dd, J=6.0 Hz, 14.3 Hz), 3.31 (1H, dd, J=6.0 Hz, 14.3 Hz), 3.73 (1H, dd, J=7.2 Hz, 7.5 Hz), 3.94-4.05 (1H, m), 4.01 (3H, s), 4.06-4.22 (1H, m), 4.34 (1H, dt, J=5.8 Hz, 8.0 Hz), 4.86 (1H, dt, J=6.0 Hz, 7.8 Hz), 5.09 (1H, d, J=7.2 Hz), 6.74 (1H, d, J=7.8 Hz), 7.26 (1H, t, J=7.3 Hz), 7.34 (1H, t, J=7.3 Hz), 7.49 (1H, s), 7.50 (1H, d, J=5.8 Hz), 7.61 (1H, d, J=7.3 Hz), 8.15 (1H, d, J=7.3 Hz)

EXAMPLE 44 Synthesis of Compound 44

Compound 44 was prepared using 1-adamantanamine instead of diisopropylamine in the same manner described in Example 33-(2).

m.p.: 129°-137° C.

IR (KBr, cm⁻¹): 3316, 2962, 2872, 1743, 1635, 1539, 1461, 1386, 1260, 1092, 747

High Resolution FAB-MS (m/e, (C₃₆ H₅₁ N₅ O₇ +H)⁺): Calcd: 666.3867 Found: 666.3879

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.61 (3H, d, J=3.9 Hz), 0.63 (3H, d, J=4.4 Hz), 0.87 (3H, t, J=6.8 Hz), 0.90-2.00 (24H, m), 2.85 (1H, dd, J=11.2 Hz, 14.4 Hz), 3.11-3.25 (1H, m), 3.83-3.95 (1H, m), 3.96 (3H, s), 4.10-4.20 (1H, m), 4.56-4.67 (1H, m), 5.63 (1H, s), 5.75 (1H, d, J=7.0 Hz), 7.25 (1H, t, J=7.5 Hz), 7.32 (1H, t, J=7.5 Hz), 7.49 (1H, s), 7.70 (1H, d, J=7.5 Hz), 8.04 (1H, d, J=7.5 Hz), 8.18 (1H, d, J=7.8 Hz), 8.31 (1H, d, J=8.7 Hz)

EXAMPLE 45 Synthesis of Compound 45

Compound 45 was prepared using D-1-aminobutyric acid benzyl ester as a starting material in the same manner described in Example 1-(2) and (3).

m.p.: 216°-218° C.

IR (KBr, cm⁻¹): 3448, 2968, 1743, 1647, 1599, 1536, 1461, 1389, 1341, 1314, 1260, 1170, 1095, 1050, 765, 747

High Resolution FAB-MS (m/e, (C₂₈ H₄₀ N₄ O₈ +H)⁺): Calcd: 561.2925 Found: 561.2911

¹ H-NMR (300 MHz, CD₃ OD, δ ppm): 0.77 (3H, d, J=6.4 Hz), 0.78 (3H, d, J=6.4 Hz), 0.87 (3H, t, J=7.4 Hz), 1.23-1.35 (2H, m), 1.37 (9H, s), 1.68-1.93 (3H, m), 3.07 (1H, dd, J=5.1 Hz, 10.7 Hz), 3.14-3.17 (1H, m), 3.95-4.02 (1H, m), 4.00 (3H, s), 4.18 (1H, dd, J=5.1 Hz, 6.5 Hz), 4.65-4.75 (1H, m), 7.24 (1H, t, J=7.7 Hz), 7.29 (1H, t, J=7.7 Hz), 7.51 (1H, s), 7.68 (1H, d, J=7.7 Hz), 8.10 (1H, d, J=7.7 Hz)

EXAMPLE 46 Synthesis of Compound 46

Compound 46 was prepared using t-butylisocyanate in the same manner described in Example 21-(3).

m.p.: 116°-121° C.

IR (KBr, cm⁻¹): 3400, 2962, 1743, 1650, 1557, 1461, 1389, 1260, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₀ H₄₅ N₅ O₇ +H)⁺): Calcd: 588.3397 Found: 588.3369

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.61 (6H, d, J=5.1 Hz), 0.87 (3H, t, J=7.0 Hz), 1.15 (9H, s), 0.82-1.89 (9H, m), 2.86 (1H, dd, J=11.3 Hz, 14.4 Hz), 3.11-3.21 (1H, m), 3.96 (3H, s), 4.09-4.21 (2H, m), 4.58-4.70 (1H, m), 5.73 (1H, d, J=9.8 Hz), 5.73 (1H, s), 7.25 (1H, t, J=7.5 Hz), 7.32 (1H, t, J=7.5 Hz), 7.50 (1H, s), 7.72 (1H, d, J=7.5 Hz), 8.04 (1H, d, J=7.8 Hz), 8.21 (1H, d, J=7.5 Hz), 8.31 (1H, d, J=8.8 Hz)

EXAMPLE 47 Synthesis of Compound 47

Compound 47 was prepared using 2-aminopyridine instead of hexamethyleneimine in the same manner described in Example 28.

m.p.: 109°-111° C.

IR (KBr, cm⁻¹): 3364, 3076, 2968, 2872, 1716, 1656, 1575, 1461, 1389, 1260, 1203, 1092, 765, 723

High Resolution FAB-MS (m/e, (C₃₁ H₄₀ N₆ O₇ +H)⁺): Calcd: 609.3036 Found: 609.3030

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.64 (3H, d, J=6.1 Hz), 0.67 (3H, d, J=6.1 Hz), 0.82 (3H, t, J=7.2 Hz), 1.05-1.38 (7H, m), 1.56-1.80 (2H, m), 2.89 (1H, dd, J=11.2 Hz, 14.6 Hz), 3.13 (1H, dd, J=1.3 Hz, 14.6 Hz), 3.96 (3H, s), 4.13-4.32 (2H, m), 4.63-4.76 (1H, m), 6.95 (1H, dd, J=5.5 Hz, 7.0 Hz), 7.26 (1H, t, J=7.7 Hz), 7.33 (1H, t, J=7.7 Hz), 7.38 (1H, d, J=8.7 Hz), 7.54 (1H, s), 7.65-7.75 (1H, m), 7.78 (1H, d, J=7.7 Hz), 7.86-8.02 (1H, m), 8.05 (1H, d, J=7.8 Hz), 8.14 (1H, dd, J=1.3 Hz, 5.5 Hz), 8.27 (1H, d, J=7.7 Hz), 8.50 (1H, d, J=8.8 Hz), 9.34 (1H, brs)

EXAMPLE 48 Synthesis of Compounds 48 and 49

Compound 48 (ester form) and Compound 49 (deprotected form) were prepared using heptamethyleneimine instead of hexamethyleneimine in the same manner described in Example 28.

Compound 48

(colorless amorphous)

IR (KBr, cm⁻¹): 3304, 2932, 2866, 1743, 1632, 1533, 1461, 1386, 1257, 1152, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₇ H₅₇ N₅ O₇ +H)⁺): Calcd: 684.4337 Found: 684.4336

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.82 (3H, t, J=7.1 Hz), 0.84 (3H, d, J=6.3 Hz), 0.85 (3H, d, J=6.3 Hz), 1.06-1.80 (19H, m), 1.41 (9H, s), 3.19 (1H, dd, J=5.9 Hz, 14.7 Hz), 3.33 (1H, dd, J=6.1 Hz, 14.7 Hz), 3.13-3.50 (4H, m), 4.01 (3H, s), 3.96-4.10 (1H, m), 4.27-4.37 (1H, m), 4.59 (1H, d, J=6.8 Hz), 4.80-4.90 (1H, m), 6.53 (1H, d, J=8.8 Hz), 6.99 (1H, d, J=7.7 Hz), 7.25 (1H, t, J=7.3 Hz), 7.33 (1H, t, J=7.3 Hz), 7.47 (1H, s), 7.62 (1H, d, J=7.3 Hz), 8.17 (1H, d, J=7.3 Hz)

Compound 49

m.p.: 99°-104° C.

IR (KBr, cm⁻¹): 3316, 2932, 2872, 1743, 1632, 1533, 1461, 1386, 1260, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₃ H₄₉ N₅ O₇ +H)⁺): Calcd: 628.3710 Found: 628.3693

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.80 (3H, d, J=5.9 Hz), 0.81 (3H, d, J=5.9 Hz), 0.83 (3H, t, J=6.0 Hz), 1.09-1.95 (19H, m), 3.05-3.46 (6H, m), 3.88-3.98 (1H, m), 4.02 (3H, s), 4.31-4.41 (1H, m), 4.77-4.86 (1H, m), 4.98 (1H, d, J=7.0 Hz), 6.63 (1H, d, J=7.4 Hz), 7.25 (1H, t, J=7.5 Hz), 7.34 (1H, t, J=7.5 Hz), 7.48 (1H, s), 7.58 (1H, d, J=7.5 Hz), 7.68 (1H, d, J=7.8 Hz), 8.16 (1H, d, J=7.5 Hz)

EXAMPLE 49 Synthesis of Compound 50

Compound 50 was prepared using H-DNva-O^(t) Bu as a starting material in the same manner described in Example 39.

m.p.: 112°-116° C.

IR (KBr, cm⁻¹): 3382, 2962, 2872, 1743, 1656, 1620, 1530, 1461, 1386, 1260

High Resolution FAB-MS (m/e, (C₃₂ H₄₇ N₅ O₇ +H)⁺): Calcd: 614.3554 Found: 614.3539

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.81 (6H, d, J=5.4 Hz), 0.84 (3H, t, J=7.3 Hz), 1.14 (3H, d, J=6.5 Hz), 1.15 (3H, d, J=6.6 Hz), 1.01-1.89 (13H, m), 3.29 (2H, d, J=5.7 Hz), 3.92-4.02 (2H, m), 4.01 (3H, s), 4.09-4.16 (1H, m), 4.28-4.35 (1H, m), 4.83 (1H, dt, J=6.3 Hz, 5.7 Hz), 4.96 (1H, d, J=4.8 Hz), 6.67-6.72 (1H, brs), 7.25 (1H, t, J=7.8 Hz), 7.34 (1H, t, J=7.8 Hz), 7.48 (1H, s), 7.58 (1H, d, J=7.8 Hz), 7.65 (1H, d, J=6.3 Hz), 8.16 (1H, d, J=7.8 Hz)

EXAMPLE 50 Synthesis of Compound 51

Compound 51 was prepared using H-DNva-O^(t) Bu as a starting material in the same manner described in Example 40.

m.p.: 115°-119° C.

IR (KBr, cm⁻¹): 3358, 2962, 2872, 1746, 1659, 1620, 1533, 1461, 1386, 1260

High Resolution FAB-MS (m/e, (C₃₃ H₄₉ N₅ O₇ +H)⁺): Calcd: 628.3732 Found: 628.3683

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.84 (9H, s), 0.84 (3H, t, J=7.2 Hz), 1.14 (6H, d, J=7.1 Hz), 1.01-1.89 (12H, m), 3.28 (1H, dd, J=5.1 Hz, 14.1 Hz), 3.32 (1H, dd, J=6.0 Hz, 14.1 Hz), 3.87-4.01 (2H, m), 4.01 (3H, s), 4.10-4.20 (1H, m), 4.32 (1H, dt, J=8.1 Hz, 4.5 Hz), 4.76 (1H, ddd, J=5.1 Hz, 6.9 Hz, 8.1 Hz), 4.98 (1H, d, J=5.4 Hz), 6.57-6.60 (1H, brs), 7.24 (1H, t, J=7.8 Hz), 7.34 (1H, t, J=7.8 Hz), 7.48 (1H, s), 7.58 (1H, d, J=7.8 Hz), 7.69 (1H, d, J=8.1 Hz), 8.16 (1H, d, J=7.8 Hz)

EXAMPLE 51 Synthesis of Compound 52

Compound 52 was prepared using H-Ile-OBzl.TsOH as a starting material in the same manner described in Example 39.

m.p.: 85°-95° C.

IR (KBr, cm⁻¹): 3328, 2968, 2872, 1743, 1671, 1539, 1461, 1386, 1344, 1311, 1260, 1203, 1149, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₃ H₄₉ N₅ O₇ +H)⁺): Calcd: 628.3710 Found: 628.3689

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.42 (3H, d, J=6.8 Hz), 0.64 (3H, t, J=7.3 Hz), 0.81-0.98 (1H, m), 0.86 (3H, t, J=7.1 Hz), 1.04 (3H, d, J=4.8 Hz), 1.06 (3H, d, J=4.8 Hz), 1.20-1.80 (14H, m), 2.84 (1H, dd, J=11.4 Hz, 14.9 Hz), 3.24 (1H, dd, J=2.6 Hz, 14.9 Hz), 3.78 (1H, t, J=7.8 Hz), 3.96 (3H, s), 4.07-4.20 (3H, m), 4.58-4.68 (1H, m), 5.94 (1H, d, J=7.8 Hz), 7.25 (1H, t, J=7.6 Hz), 7.32 (1H, t, J=7.6 Hz), 7.52 (1H, s), 7.66 (1H, d, J=7.6 Hz), 8.04 (1H, d, J=7.6 Hz), 8.27 (1H, d, J=7.8 Hz), 8.31 (1H, d, J=8.7 Hz)

Each Compound 53 and 54 in the following Example 52 and 53 was prepared using each corresponding amino acid benzyl ester tosylate as a starting material in the same manner described in Example 51.

EXAMPLE 52 Compound 53

m.p.: 85°-94° C.

IR (KBr, cm⁻¹): 3328, 2968, 2872, 1743, 1671, 1530, 1461, 1386, 1344, 1311, 1260, 1200, 1149, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₃ H₄₉ N₅ O₇ +H)⁺): Calcd: 628.3710 Found: 628.3698

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.51 (3H, d, J=6.5 Hz), 0.60 (3H, t, J=7.1 Hz), 0.80-0.92 (1H, m), 0.86 (3H, t, J=7.0 Hz), 1.04 (3H, d, J=6.2 Hz), 1.06 (3H, d, J=6.2 Hz), 1.20-1.80 (14H, m), 2.83 (1H, dd, J=11.7 Hz, 14.7 Hz), 3.23 (1H, dd, J=2.8 Hz, 14.7 Hz), 3.88 (1H, t, J=7.7 Hz), 3.96 (3H, s), 4.02-4.18 (3H, m), 4.59-4.69 (1H, m), 5.78 (1H, d, J=7.7 Hz), 7.25 (1H, t, J=7.6 Hz), 7.32 (1H, t, J=7.6 Hz), 7.53 (1H, s), 7.69 (1H, d, J=7.6 Hz), 8.04 (1H, d, J=7.6 Hz), 8.27 (1H, d, J=7.52 Hz), 8.32 (1H, d, J=9.1 Hz)

EXAMPLE 53 Compound 54

m.p.: 108°-111° C.

IR (KBr, cm⁻¹): 3340, 2962, 2872, 1743, 1650, 1632, 1518, 1461, 1386, 1260, 1146, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₃ H₄₉ N₅ O₇ +H)⁺): Calcd: 628.3711 Found: 628.3705

¹ H-NMR (400 MHz, CDCl₃, δ ppm): 0.81 (3H, t, J=6.8 Hz), 0.91 (9H, s), 1.19 (6H, d, J=6.8 Hz), 1.12-1.36 (4H, m), 1.43-1.87 (8H, m), 3.25 (1H, dd, J=5.9 Hz, 15.6 Hz), 3.34 (1H, dd, J=6.8 Hz, 15.6 Hz), 3.87-4.00 (1H, m), 4.01 (3H, s), 4.01-4.06 (1H, m), 4.13-4.18 (1H, m), 4.35-4.40 (1H, m), 4.81-4.87 (1H, m), 5.12 (1H, d, J=7.8 Hz), 6.76-6.82 (1H, brs), 7.27 (1H, t, J=7.8 Hz), 7.35 (1H, t, J=7.8 Hz), 7.39-7.42 (1H, brs), 7.50 (1H, s), 7.63 (1H, d, J=7.8 Hz), 8.17 (1H, d, J=7.8 Hz)

EXAMPLE 54 Synthesis of Compound 55

Compound 55 was prepared using 2-(2-chlorophenyl)carbamoyloxy-4-methylpentanoic acid, which was prepared using 2-hydroxy-5-methylpentanoic acid instead of H-Leu-OBzl in the same manner described in Example 18-(2), as a starting material in the same manner described in Example 33-(3).

m.p.: 161°-163° C.

IR (KBr, cm⁻¹): 3310, 2962, 1740, 1659, 1533, 1461, 1449, 1386, 1260, 1212, 1089, 747

High Resolution FAB-MS (m/e, (C₃₂ H₃₉ ClN₄ O₈ +H)⁺): Calcd: 643.2535 Found: 643.2511

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.82 (3H, t, J=7.0 Hz), 0.91 (6H, d, J=4.5 Hz), 1.13-1.31 (4H, m), 1.56-1.84 (5H, m), 3.16 (1H, dd, J=14.5 Hz, 7.2 Hz), 3.29 (1H, dd, J=14.5 Hz, 6.7 Hz), 3.96 (3H, s), 4.41-4.48 (1H, m), 4.78-4.86 (1H, m), 5.04-5.09 (1H, m), 6.60 (1H, d, J=7.6 Hz), 6.78 (1H, d, J=7.7 Hz), 7.02 (1H, t, J=7.7 Hz), 7.18-7.30 (4H, m), 7.35 (1H, d, J=7.7 Hz), 7.48 (1H, s), 7.62 (1H, d, J=6.3 Hz), 7.99 (1H, d, J=8.0 Hz), 8.08 (1H, d, J=7.7 Hz)

EXAMPLE 55 Synthesis of Compound 56

Compound 56 was prepared using H-DVal-OBzl.TsOH instead of H-DNle-OBzl.TsOH in the same manner described in Example 1-(2) and (3).

m.p.: 203°-207° C.

IR (KBr, cm⁻¹): 3328, 2968, 1722, 1695, 1530, 1461, 1389, 1260, 1170, 1092, 765

High Resolution FAB-MS (m/e, (C₂₉ H₄₂ N₄ O₈ +H)⁺): Calcd: 575.3081 Found: 575.3066

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (3H, d, J=6.4 Hz), 0.67 (3H, d, J=6.4 Hz), 0.85 (3H, d, J=6.9 Hz), 0.86 (3H, d, J=6.9 Hz), 0.90-1.48 (3H, m), 1.31 (9H, s), 2.00-2.14 (1H, m), 2.91 (1H, dd, J=10.3 Hz, 14.7 Hz), 3.12 (1H, dd, J=3.0 Hz, 14.7 Hz), 3.85-4.00 (1H, m), 3.95 (3H, s), 4.04 (1H, dd, J=5.2 Hz, 7.9 Hz), 4.60-4.71 (1H, m), 6.68 (1H, d, J=8.1 Hz), 7.23 (1H, t, J=7.5 Hz), 7.31 (1H, t, J=7.5 Hz), 7.50 (1H, s), 7.69 (1H, d, J=7.5 Hz), 7.80 (1H, d, J=7.9 Hz), 8.04 (1H, d, J=7.5 Hz), 8.16 (1H, d, J=8.0 Hz)

EXAMPLE 56 Synthesis of Compound 57 and 58 (1) Preparation of Boc-DTrp(COOMe)φ(CS-NH)-DNle-O^(t) Bu

Boc-DTrp(COOMe)-DNle-O^(t) Bu (300 mg, prepared in Example 21-(1)) and Lawesson's Reagent (140 mg) were suspended in toluene. The mixture was stirred at 100° C. under argon atmosphere for 5 h and concentrated under reduced pressure. The residue was purified by silica gel chromatography (Merck, Kieselgel 60) with chloroform/diethyl ether=99/1 for elution to give the product (172 mg).

FAB-MS (m/e, (C₂₈ H₄₁ N₃ O₆ S+H)⁺): 547

(2) Preparation of Compound 57

A solution of Boc-DTrp(COOMe)φ(CS-NH)-DNle-O^(t) Bu (100 mg, obtained in (1)) in formic acid (3 ml) was stirred at room temperature for 2 h and concentrated under reduced pressure. The residue was dissolved in DMF (2 ml), and NMM (100 μl) was added. To the mixture were added 2,6-dimethylpiperidinocarbonyl-γMeLeu-OH (52 mg), HOBT.H₂ O (34 mg) and EDCI.HCl (42 mg) under ice cooling. The mixture was stirred at the same temperature for 30 min and at room temperature for 14 h. The reaction mixture was diluted with ethyl acetate, washed with sat. aq NaHCO₃, 1N-hydrochloric acid and water successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with hexane/ethyl acetate=3/2 for development to give Compound 57 (28 mg).

m.p.: 75°-78° C.

IR (KBr, cm⁻¹): 3256, 2956, 2872, 1743, 1626, 1518, 1461, 1374, 1341, 1311, 1257, 1227, 1158, 1089, 1041, 765, 747

High Resolution FAB-MS (m/e, (C₃₈ H₅₉ N₅ O₆ S+H)⁺): Calcd: 714.4264 Found: 714.4252

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.82 (3H, t, J=7.2 Hz), 0.90 (9H, s), 0.95-1.92 (14H, m), 1.19 (3H, d, J=7.1 Hz), 1.20 (3H, d, J=7.1 Hz), 1.37 (9H, s), 3.29 (1H, dd, J=7.2 Hz, 14.4 Hz), 3.47 (1H, dd, J=5.5 Hz, 14.4 Hz), 4.00 (3H, s), 4.05-4.13 (1H, m), 4.11-4.22 (1H, m), 4.19-4.26 (1H, m), 4.65 (1H, d, J=7.4 Hz), 4.72-4.79 (1H, m), 4.97 (1H, ddd, J=5.5 Hz, 7.2 Hz, 8.0 Hz), 7.06 (1H, d, J=8.0 Hz), 7.26 (1H, t, J=7.4 Hz), 7.33 (1H, t, J=7.4 Hz), 7.49 (1H, s), 7.72 (1H, d, J=7.4 Hz), 8.15 (2H, d, J=7.4 Hz)

(3) Preparation of Compound 58

Compound 57 (13 mg, prepared in (2)) was dissolved in formic acid (1 ml) under ice cooling, and the mixture was stirred at the same temperature for 1.5 h and at room temperature for 6 h. The mixture was diluted with ethyl acetate, washed with brine and water, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel chromatography (Wakogel C-200) with chloroform/methanol=97/3 for elution to give Compound 58 (7.3 mg).

m.p.: 74°-82° C.

IR (KBr, cm⁻¹): 3310, 2956, 2866, 1743, 1620, 1572, 1524, 1461, 1386, 1341, 1260, 1230, 1128, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₄ H₅₁ N₅ O₆ S+H)⁺): Calcd: 658.3638 Found: 658.3658

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.78 (9H, s), 0.86 (3H, t, J=6.8 Hz), 0.92-2.05 (14H, m), 1.14 (6H, d, J=7.1 Hz), 3.33 (1H, dd, J=7.9 Hz, 14.7 Hz), 3.54 (1H, dd, J=5.3 Hz, 14.7 Hz), 3.92-4.06 (2H, m), 3.99 (3H, s), 4.09-4.16 (1H, m), 4.94-5.07 (2H, m), 5.17 (1H, ddd, J=5.3 Hz, 6.3 Hz, 7.9 Hz), 6.99 (1H, d, J=6.3 Hz), 7.22 (1H, t, J=7.8 Hz), 7.31 (1H, t, J=7.8 Hz), 7.51 (1H, s), 7.64 (1H, d, J=7.8 Hz), 8.11 (1H, d, J=7.8 Hz), 8.89 (1H, d, J=7.5 Hz)

EXAMPLE 57 Synthesis of Compound 59 (1) Preparation of 2-hydroxy-3-(3-indolyl)propionyl-DNle-O^(t) Bu

To a solution of DL-3-indolelactic acid (103 mg), H-DNle-O^(t) Bu.HCl (100 mg) and NMM (58 μl) in dichloromethane (5.0 ml) were added HOBT.H₂ O (81 mg) and EDCI.HCl (102 mg) under ice cooling. After being stirred at room temperature over night, the mixture was diluted with dichloromethane (20 ml), washed with sat. aq NaHCO₃, 10% aq. citric acid and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by MPLC (Merck, LiChroprep Si 60) with hexane/ethyl acetate=3/2 for elution to give the product (80 mg).

FAB-MS (m/e, (C₂₁ H₃₀ N₂ O₄ +H)⁺): 375

(2) Preparation of 2,6-dimethylpiperidinocarbonyl-γMeLeu-φ(COO)-DTrp-DNle-O^(t) Bu

To a solution of 2-hydroxy-3-(3-indolyl)propionyl-DNle-O^(t) Bu (62 mg, prepared in (1)) and 2,6-dimethylpiperidinocarbonyl-γMeLeu-OH (72 mg) in THF (1.5 ml) were added EDCI.HCl (48 mg) and DMAP (10 mg) under ice cooling. The mixture was stirred at room temperature for 3 d, and concentrated under reduced pressure. To the residue was added water (20 ml), and the mixture was extracted with ethyl acetate (10 ml×3). The combined organic layers were washed with 1N-hydrochloric acid (10 ml), sat. aq. NaHCO₃ and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by MPLC (Merck, LiChroprep Si 60) with hexane/ethyl acetate=2/1 for elution to give the product (91 mg).

FAB-MS (m/e, (C₃₆ H₅₆ N₄ O₆ +H)⁺): 641

(3) Preparation of 2,6-dimethylpiperidinocarbonyl-γMeLeu-φ(COO)-DTrp(COOMe)-DNle-O.sup.t Bu

To a solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-φ(COO)-DTrp-DNle-O^(t) Bu (76 mg, prepared in (2)) in dichloromethane were added methyl chloroformate (14 μl), pulverized NaOH (12 mg) and TBAHS (1 mg) under ice cooling. After being stirred at room temperature for 6 h, the mixture was diluted with dichloromethane (30 ml). The solution was washed with water (20 ml), dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with hexane/ethyl acetate=2/1 for development to give the compound (41 mg).

FAB-MS (m/e, (C₃₈ H₅₈ N₄ O₈ +H)⁺): 699

(4) Preparation of Compound 59

A solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-φ(COO)-DTrp(COOMe)-DNle-O.sup.t Bu (36 mg, prepared in (3)) in TFA (3 ml) was stirred at room temperature for 1 h, and concentrated under reduced pressure. The residue was triturated with water to give Compound 59 (32 mg).

m.p.: 74°-79° C.

IR (KBr, cm⁻¹): 3406, 2962, 1746, 1671, 1629, 1539, 1461, 1386, 1260, 1200, 1164, 1092, 765, 747

FAB-MS (m/e, (C₃₄ H₅₀ N₄ O₈ +H)⁺): 643

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.83 (3H, t, J=7.2 Hz), 0.89 (9H, s), 1.00-1.90 (14H, m), 1.17 (3H, d, J=7.5 Hz), 1.20 (3H, d, J=7.5 Hz), 3.31 (1H, dd, J=7.5 Hz, 14.9 Hz), 3.40 (1H, dd, J=3.8 Hz, 14.9 Hz), 3.70-4.10 (2H, m), 4.02 (3H, s), 4.07-4.19 (1H, m), 4.30-4.40 (1H, m), 5.48 (1H, dd, J=3.8 Hz, 7.5 Hz), 7.25 (1H, t, J=7.5 Hz), 7.34 (1H, t, J=7.5 Hz), 7.48 (1H, s), 7.59 (1H, d, J=7.5 Hz), 7.20-8.00 (2H, brs), 8.16 (1H, d, J=7.5 Hz)

EXAMPLE 58 Synthesis of Compound 60

Compound 60 was prepared in the same manner described in Example 50.

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.82 (3H, t, J=7.2 Hz), 0.89 (9H, s), 1.15 (3H, d, J=7.1 Hz), 1.05-1.75 (14H, m), 1.16 (3H, d, J=7.1 Hz), 1.41 (9H, s), 3.17 (1H, dd, J=6.2 Hz, 15.0 Hz), 3.37 (1H, dd, J=5.9 Hz, 15.0 Hz), 3.93-4.10 (2H, m), 4.00 (3H, s), 4.10-4.23 (1H, m), 4.24-4.36 (1H, m), 4.65 (1H, d, J=7.1 Hz), 4.81 (1H, ddd, J=5.9 Hz, 6.2 Hz, 8.5 Hz), 6.48 (1H, d, J=8.5 Hz), 7.03 (1H, d, J=7.6 Hz), 7.24 (1H, t, J=7.6 Hz), 7.33 (1H, t, J=7.6 Hz), 7.47 (1H, s), 7.62 (1H, d, J=7.6 Hz), 8.16 (1H, d, J=7.8 Hz)

EXAMPLE 59 Synthesis of Compounds 61, 62, 63 and 64 (1) Preparation of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DLmTyr-DNle-OBzl

The title compound was prepared from 2,6-dimethylpiperidinocarbonyl-γMeLeu-OH, Boc-DLmTyr-OH and H-DNle-OBzl according to the same procedure described in Example 14.

FAB-MS (m/e, (C₃₇ H₅₄ N₄ O₆ +H)⁺): 651

(2) Preparation of Compound 61

Compound 61 was prepared by deprotection of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DLmTyr-DNle-OBzl in a similar manner to that of Example 1-(3).

IR (KBr, cm⁻¹): 3328, 2956, 2872, 1602, 1533, 1464, 1404, 1341, 1251

FAB-MS (m/e, (C₃₀ H₄₈ N₄ O₆ +H)⁺): 561

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.81 (3H, t, J=6.1 Hz), 0.84 (9H, s), 1.13 (6H, d, J=7.0 Hz), 1.03-1.85 (14H, m), 2.80-2.99 (1H, m), 2.99-3.13 (1H, m), 3.95-4.30 (4H, m), 4.53-4.71 (1H, m), 6.63 (1H, d, J=7.6 Hz), 6.68 (1H, d, J=7.6 Hz), 6.79 (1H, brs), 7.05 (1H, t, J=7.6 Hz), 7.46 (1H, brs)

(3) Preparation of Compound 62

2,6-dimethylpiperidinocarbonyl-γMeLeu-DLmTyr-DNle-OBzl (prepared in (1)) was acetylated by acetic anhydride and DMAP in THF. The product was deprotected in a similar manner to that of Example 1-(3) to afford Compound 63.

FAB-MS (m/e, (C₃₂ H₅₀ N₄ O₇ +H)⁺): 603

(4) Preparation of Compound 63

2,6-dimethylpiperidinocarbonyl-γMeLeu-DLmTyr-DNle-OBzl (prepared in (1)) was methylated by etherial diazomethane. The product was deprotected in a similar manner to that of Example 1-(3) to afford Compound 64.

FAB-MS (m/e, (C₃₁ H₅₀ N₄ O₆ +H)⁺): 575

(5) Preparation of Compound 64

2,6-dimethylpiperidinocarbonyl-γMeLeu-DLmTyr-DNle-OBzl (prepared in (1)) was methoxycarbonylated by methyl chloroformate and DMAP in THF. The product was deprotected in a similar manner to that of Example 1-(3) to afford Compound 63.

FAB-MS (m/e, (C₃₂ H₅₀ N₄ O₈ +H)⁺): 619

EXAMPLE 60 Synthesis of Compound 65

Compound 65 was prepared using DSer as a starting material in the same manner described in Example 6.

IR (KBr, cm⁻¹): 3328, 2962, 1743, 1659, 1563, 1461, 1386, 1260, 1167, 1092, 1050, 762

High Resolution FAB-MS (m/e, (C₂₇ H₃₈ N₄ O₉ +H)⁺): Calcd: 563.2717 Found: 563.2694

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.67 (3H, d, J=6.6 Hz), 0.69 (3H, d, J=6.6 Hz), 0.98-1.38 (3H, m), 1.31 (9H, s), 2.93 (1H, dd, J=9.7 Hz, 14.6 Hz), 3.13 (1H, dd, J=4.2 Hz, 14.6 Hz), 3.26-3.36 (1H, m), 3.51-3.60 (1H, m), 3.73-3.85 (1H, m), 3.89-4.01 (1H, m), 3.94 (3H, s), 4.55-4.68 (1H, m), 6.68 (1H, d, J=8.0 Hz), 7.22 (1H, t, J=7.8 Hz), 7.30 (1H, t, J=7.5 Hz), 7.48 (1H, s), 7.69 (1H, d, J=7.5 Hz), 7.69 (1H, d, J=7.5 Hz), 8.03 (1H, d, J=7.5 Hz), 8.19 (1H, d, J=7.5 Hz)

EXAMPLE 61 Synthesis of Compound 66 (1) Preparation of N-(2-thienylcarbamoyl)-γMeLeu-OBzl

To a solution of 2-thiophenecarboxylic acid (30 mg) and diphenylphosphoryl azide (50.5 μl) in toluene (10 ml) was added TEA (32.6 μl) under ice cooling. The mixture was stirred at the same temperature for 1 h, at room temperature for 10 h and refluxed for 6 h. The mixture was cooled to room temperature. To the mixture was added a solution of γMeLeu-OBzl.TsOH (61 mg) and TEA (21 μl) in DMF (1 ml). After being stirred at room temperature for 15 h, the reaction mixture was diluted with ethyl acetate, washed with sat. aq. NaHCO₃, 1N-hydrochloric acid and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with hexane/ethyl acetate=4/1 for development to give the product.

FAB-MS (m/e, (C₁₉ H₂₄ N₂ O₃ S+H)⁺): 361

(2) Preparation of Compound 66

N-(2-Thienylcarbamoyl)-γMeLeu-OBzl (27.0 mg, prepared in (1)) was hydrolyzed with aqueous sodium hydroxide in methanol to afford N-(2-thienylcarbamoyl)-γMeLeu-OH (22.0 mg), which was condensed with H-DTrp(COOMe)-DNle-O^(t) Bu.HCl (35.0 mg, prepared in Example 21-(1)) in a similar manner to that of Example 33-(3) to afford Compound 66 (5.4 mg).

High Resolution FAB-MS (m/e, (C₃₁ H₄₁ N₅ O₇ S+H)⁺): Calcd: 628.2805 Found: 628.2822

Each compound 67-70 in the following Examples 62-65 was prepared using each corresponding amine and amino acid benzyl ester tosylate in the same manner described in Example 36.

EXAMPLE 62 Compound 67

m.p.: 98°-102° C.

IR (KBr, cm⁻¹): 3316, 2962, 2872, 1743, 1632, 1521, 1461, 1386, 1260, 1092, 765, 747

High Resolution FAB-MS (m/e, (C₃₁ H₄₅ N₅ O₇ +H)⁺): Calcd: 600.3397 Found: 600.3371

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.50 (3H, d, J=6.7 Hz), 0.57 (3H, d, J=6.7 Hz), 0.86 (3H, t, J=6.8 Hz), 1.10 (6H, d, J=5.6 Hz), 0.92-2.10 (11H, m), 2.84 (1H, dd, J=11.2 Hz, 14.4 Hz), 3.21 (1H, dd, 3.1 Hz, 14.4 Hz), 3.67-3.90 (3H, m), 3.96 (3H, s), 4.08-4.20 (1H, m), 4.57-4.72 (1H, m), 5.47 (1H, d, J=7.8 Hz), 7.25 (1H, t, J=7.6 Hz), 7.32 (1H, t, J=7.6 Hz), 7.52 (1H, s), 7.69 (1H, d, J=7.6 Hz), 8.03 (1H, d, J=7.6 Hz), 8.31 (1H, d, J=8.1 Hz), 8.35 (1H, d, J=9.0 Hz)

EXAMPLE 63 Compound 68

IR (KBr, cm⁻¹): 2954, 2859, 1737, 1616, 1525, 1442, 1340, 1309, 1226, 1199, 1126, 765, 748

High Resolution FAB-MS (m/e, (C₃₃ H₄₇ N₅ O₇ +H)⁺): Calcd: 626.3554 Found: 626.3572

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): -0.80-0.95 (2H, m), 0.01-0.39 (3H, m), 0.86 (3H, t, J=7.0 Hz), 1.03 (3H, d, J=7.4 Hz), 1.05 (3H, d, J=7.4 Hz), 0.98-1.82 (14H, m), 2.85 (1H, dd, J=10.9 Hz, 14.7 Hz), 3.22 (1H, dd, 3.1 Hz, 14.7 Hz), 3.95 (3H, s), 3.90-4.20 (4H, m), 4.53-4.65 (1H, m), 6.05 (1H, d, J=6.8 Hz), 7.24 (1H, t, J=7.4 Hz), 7.31 (1H, t, J=7.4 Hz), 7.49 (1H, s), 7.68 (1H, d, J=7.4 Hz), 8.02 (1H, d, J=7.4 Hz), 8.24 (1H, d, J=6.9 Hz), 8.25 (1H, d, J=8.8 Hz)

EXAMPLE 64 Compound 69

m.p.: 103°-113° C.

IR (KBr, cm⁻¹): 2958, 2937, 1737, 1654, 1618, 1527, 1477, 1444, 1382, 1340, 1309, 1259, 1226, 1201, 1145, 1126, 765

High Resolution FAB-MS (m/e, (C₃₂ H₄₅ N₅ O₇ +H)⁺): Calcd: 612.3397 Found: 612.3384

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.02-0.39 (4H, m), 0.79-0.97 (1H, m), 0.84 (3H, t, J=7.0 Hz), 1.04 (3H, d, J=6.7 Hz), 1.06 (3H, d, J=6.7 Hz), 1.12-1.78 (12H, m), 2.85 (1H, dd, J=10.9 Hz, 14.7 Hz), 3.21-3.37 (2H, m), 3.96 (3H, s), 4.02-4.21 (3H, m), 4.50-4.62 (1H, m), 6.27 (1H, d, J=5.6 Hz), 7.26 (1H, t, J=7.4 Hz), 7.33 (1H, t, J=7.4 Hz), 7.52 (1H, s), 7.65 (1H, d, J=7.4 Hz), 8.05 (1H, d, J=7.4 Hz), 8.20 (1H, d, J=6.8 Hz), 8.21 (1H, d, J=9.3 Hz)

EXAMPLE 65 Compound 70

IR (KBr, cm⁻¹): 2954, 2861, 1737, 1650, 1531, 1444, 1413, 1342, 1299, 1224, 1091, 765, 746

High Resolution FAB-MS (m/e, (C₃₃ H₄₇ N₅ O₇ +H)⁺): Calcd: 626.3554 Found: 626.3538

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.76-0.96 (3H, m), 0.96-2.30 (23H, m), 2.73-2.90 (1H, m), 3.00-3.61 (5H, m), 3.61-3.75 (1H, m), 3.96 (3H, s), 4.03-4.20 (1H, m), 4.49-4.63 (1H, m), 5.97 (1H, d, J=4.9 Hz), 7.16-7.38 (2H, m), 7.53 (1H, s), 7.65 (1H, d, J=7.2 Hz), 8.05 (1H, d, J=7.2 Hz), 8.24 (1H, d, J=6.5 Hz), 8.32 (1H, d, J=7.7 Hz)

EXAMPLE 66 Synthesis of Compound 71

Compound 71 was prepared using DSer(Me) as a starting material in the same manner described in Example 6.

m.p.: 103°-106° C.

IR (KBr, cm⁻¹): 3328, 2962, 1743, 1527, 1461, 1386, 1344, 1260, 1167, 1092, 1047, 1023, 765

High Resolution FAB-MS (m/e, (C₂₈ H₄₀ N₄ O₉ +H)⁺): Calcd: 577.2874 Found: 577.2885

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.65 (3H, d, J=6.3 Hz), 0.67 (3H, d, J=6.3 Hz), 1.31 (9H, s), 0.90-1.60 (3H, m), 2.80-3.20 (2H, m), 3.27 (3H, s), 3.43-3.75 (2H, m), 3.83-4.02 (1H, m), 3.95 (3H, s), 4.39-4.51 (1H, m), 4.65-4.81 (1H, m), 6.67 (1H, d, J=7.1 Hz), 7.23 (1H, dt, J=1.3 Hz, 7.6 Hz), 7.31 (1H, dt, J=1.3 Hz, 7.6 Hz), 7.51 (1H, s), 7.73 (1H, dd, J=1.3 Hz, 7.6 Hz), 8.03 (1H, dd, J=1.3 Hz, 7.6 Hz), 8.17 (1H, d, J=8.3 Hz), 8.37 (1H, d, J=8.3 Hz)

EXAMPLE 67 Synthesis of Compounds 72, 73, 74 and 75 (1) Preparation of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DPhe(m-NO₂)-DNle-O^(t) Bu

The title compound was prepared from 2,6-dimethylpiperidinocarbonyl-γMeLeu-OH, BOc-DPhe(m-NO₂)-OH and H-DNle-O^(t) Bu.HCl according to the same manner described in Example 14.

FAB-MS (m/e, (C₃₄ H₅₅ N₅ O₇ +H)⁺): 646

(2) Preparation of Compound 72

A solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DPhe(m-NO₂)-DNle-O^(t) Bu (34 mg, prepared in (1)) in 4N-hydrogen chloride/1,4-dioxane (3 ml) was stirred at room temperature for 2 h. The mixture was evaporated in vacuo and the residue was triturated with diethyl ether to give Compound 72 (24 mg).

IR (KBr, cm⁻¹): 3376, 2956, 2872, 1725, 1668, 1536, 1473, 1452, 1356, 1248, 1200, 1140

High Resolution FAB-MS (m/e, (C₃₀ H₄₇ N₅ O₇ +H)⁺): Calcd: 590.3554 Found: 590.3580

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.80-1.8 (17H, m), 0.87 (9H, s), 1.15 (6H, d, J=7.0 Hz), 3.12-3.42 (2H, m), 4.0-4.85 (6H, m), 6.88 (1H, d, J=7.7 Hz), 7.06 (1H, d, J=7.7 Hz), 7.46 (1H, t, J=7.8 Hz), 7.61-7.64 (1H, m), 8.04-8.11 (2H, m)

(3) Preparation of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DPhe(m-NH₂)-DNle-O^(t) Bu

A solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DPhe(m-NO₂)-DNle-O^(t) Bu (285 mg, prepared in (1)) in 95% ethanol (10 ml) was hydrogenated over 10% Pd/C at an atmospheric pressure of hydrogen for 3 h. After removal of the catalyst by filtration, the filtrate was evaporated in vacuo to give the product (274 mg).

FAB-MS (m/e, C₃₄ H₅₇ N₅ O₅ +H)⁺): 616

(4) Preparation of Compound 73 Hydrochloride

Deprotection of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DPhe(m-NH₂)-DNle-O^(t) Bu (31 mg, prepared in (3)) in a similar manner to that of Example 67-(2) gave Compound 73 hydrochloride (28 mg).

m.p.: 144°-148° C.

IR (KBr, cm⁻¹): 3400, 2954, 1774, 1720, 1655, 1531, 1466, 1389, 1246, 1205, 1140, 689

High Resolution FAB-MS (m/e, (C₃₀ H₄₉ N₅ O₅ +H)⁺): Calcd: 560.3812 Found: 560.3842

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.80 (9H, s), 0.86 (3H, t, J=7.0 Hz), 1.04 (3H, d, J=7.2 Hz), 1.07 (3H, d, J=7.2 Hz), 1.12-1.81 (14H, m), 2.75 (1H, dd, J=10.5 Hz, 13.6 Hz), 3.18 (1H, dd, J=3.5 Hz, 13.6 Hz), 4.01-4.25 (4H, m), 4.36-4.49 (1H, m), 6.14 (1H, d, J=6.6 Hz), 7.14-7.34 (4H, m), 8.14 (1H, d, J=8.8 Hz), 8.23 (1H, d, J=7.6 Hz), 10.5 (3H, brs)

(5) Preparation of Compound 74

To a solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DPhe(m-NH₂)-DNle-O^(t) Bu (31 mg, prepared in (3)) in dichloromethane (1 ml) were added DMAP (10 mg) and formic pivalic anhydride (20 μl), and the mixture was stirred at room temperature for 20 h. The mixture was diluted with dichloromethane (30 ml), washed with 1N-aqueous sodium hydroxide (20 ml), 1N-hydrochloric acid (20 ml) and brine (20 ml) successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with hexane/ethyl acetate=1/2 for development to give ^(t) Bu ester of Compound 74 (23 mg). The product (20 mg) was deprotected in a similar manner to that of Example 67-(2) to give Compound 74 (16 mg).

m.p.: 123°-125° C.

IR (KBr, cm⁻¹): 3300, 2953, 2800, 1774, 1670, 1614, 1535, 1446, 1396, 1369, 1248, 1142, 789, 690

High Resolution FAB-MS (m/e, (C₃₁ H₄₉ N₅ O₆ +H)⁺): Calcd: 588.3761 Found: 588.3759

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.79 (9H, s), 0.86 (3H, t, J=7.0 Hz), 0.96-1.80 (23H, m), 2.62-2.75 (1H, m), 3.05-3.17 (1H, m), 3.83-4.49 (3H, m), 6.05 (1H, brs), 6.95 (1H, d, J=7.6 Hz), 7.06-7.23 (2H, m), 7.42 (1H, s), 8.15 (1H, d, J=7.3 Hz), 8.22 (1H, d, J=1.7 Hz), 10.07 (1H, brs)

(6) Preparation of Compound 75

To a solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DPhe(m-NH₂)-DNle-O^(t) Bu (31 mg, prepared in (3)) in dichloromethane (1 ml) were added DMAP (10 mg) and methyl chloroformate (12 μl), and the mixture was stirred at room temperature for 12 h. The mixture was diluted with dichloromethane (30 ml), washed with 1N-aqueous sodium hydroxide (20 ml), 1N-hydrochloric acid (20 ml) and brine (20 ml) successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with hexane/ethyl acetate=1/1 for development to give ^(t) Bu ester of Compound 75 (26 mg). The product (23 mg) was deprotected in a similar manner to that of Example 67-(2) to give Compound 75 (16 mg).

m.p.: 116°-118° C.

IR (KBr, cm⁻¹): 3300, 2954, 2858, 1774, 1716, 1668, 1614, 1547, 1448, 1232, 1074, 773

High Resolution FAB-MS (m/e, (C₃₂ H₅₁ N₅ O₇ +H)⁺): Calcd: 618.3867 Found: 618.3865

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.79 (9H, s), 0.86 (3H, t, J=7.0 Hz), 1.04 (3H, d, J=6.3 Hz), 1.06 (3H, d, J=6.3 Hz), 0.98-1.78 (14H, m), 2.64 (1H, dd, J=11.1 Hz, 13.4 Hz), 3.08 (1H, dd, J=3.3 Hz, 13.4 Hz), 3.63 (3H, s), 3.99-4.43 (5H, m), 6.05 (1H, d, J=7.4 Hz), 6.86 (1H, d, J=7.8 Hz), 7.08 (1H, t, J=7.8 Hz), 7.24 (1H, d, J=7.8 Hz), 7.30 (1H, s), 8.06-8.18 (2H, m), 9.49 (1H, s)

EXAMPLE 68 Synthesis of Compounds 76 and 77

Compounds 76 and 77 were prepared using 2,6-dimethylpiperidinocarbonyl-γMeLeu-OH as a starting material in the same manner described in Example 18.

Compound 76

High Resolution FAB-MS (m/e, (C₃₆ H₅₆ N₄ O₅ S+H)⁺): Calcd: 657.4050 Found: 657.4042

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.84 (3H, t, J=7.4 Hz), 0.89 (9H, s), 1.10-1.75 (14H, m), 1.168 (3H, d, J=7.1 Hz), 1.173 (3H, d, J=7.1 Hz), 1.41 (9H, s), 3.37 (1H, dd, J=6.4 Hz, 14.6 Hz), 3.48 (1H, dd, J=6.6 Hz, 14.6 Hz), 3.96-4.08 (2H, m), 4.13-4.23 (1H, m), 4.29 (1H, ddd, J=5.7 Hz, 7.8 Hz, 7.8 Hz), 4.66 (1H, d, J=6.8 Hz), 4.83 (1H, ddd, J=6.4 Hz, 6.6 Hz, 8.5 Hz), 6.53 (1H, d, J=8.5 Hz), 6.95 (1H, d, J=7.8 Hz), 7.26 (1H, s), 7.30-7.40 (2H, m), 7.81-7.88 (2H, m)

Compound 77

IR (KBr, cm⁻¹): 2775, 1712, 1666, 1531, 1429, 1203, 1138, 800, 762, 721

High Resolution FAB-MS (m/e, (C₃₂ H₄₈ N₄ O₅ S+H)⁺): Calcd: 601.3423 Found: 601.3406

¹ H-NMR (300 MHz, CD₃ OD, δ ppm): 0.84 (9H, s), 0.8-1.9 (17H, m), 1.16 (6H, d, J=7.1 Hz), 3.2-3.5 (2H, m), 4.08-4.38 (4H, m), 4.8-4.9 (1H, m), 7.28-7.41 (2H, m), 7.31 (1H, s), 7.83-7.90 (2H, m)

EXAMPLE 69 Synthesis of Compound 78 and 79 (1) Preparation of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(OH)-DNle-O^(t) Bu

To a solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp-DNle-O^(t) Bu (128 mg) in acetic acid (1.0 ml) was added sodium cyanoborohydride (126 mg). The mixture was stirred at room temperature for 17 h, and water (10 ml) was added to the mixture. The mixture was extracted with ethyl acetate (10 ml×3). The combined organic layers were washed with sat. aq. NaHCO₃ (3 ml), dried over MgSO₄ and evaporated in vacuo. The residue was purified by MPLC (Merck, LiChroprep Si 60) with hexane/ethyl acetate=1/1 for elution to give a colorless powder (58.2 mg). To a solution of the product (32.1 mg) and sodium tungustate dihydrate (3.3 mg) in methanol (1.0 ml) and water (0.3 ml) was added 30% hydrogen peroxide (51 μl). After being stirred at room temperature for 1 h, the mixture was evaporated in vacuo. The residue was purified by silica gel chromatography (Wakogel, C-200) with hexane/ethyl acetate=1/1 for elution to give the product (13.7 mg).

FAB-MS (m/e, (C₃₆ H₅₇ N₅ O₆ +H)⁺): 656

(2) Preparation of Compound 78

A solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(OH)-DNle-O^(t) Bu (11 mg, prepared in (1)) in formic acid (0.4 ml) was stirred at room temperature for 13 h. The mixture was concentrated under reduced pressure, and the residue was purified by preparative TLC (3M, Empore Silica Sheet) with chloroform/methanol/acetic acid=20/1/1 for development to give the product (3.4 mg).

m.p.: 165° C. (dec.)

High Resolution FAB-MS (m/e, (C₃₂ H₄₉ N₅ O₆ +H)⁺): Calcd: 600.3761 Found: 600.3774

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.80 (9H, s), 1.05 (6H, d, J=6.8 Hz), 0.80-1.80 (17H, m), 2.84 (1H, dd, J=9.7 Hz, 14.4 Hz), 3.10-3.20 (1H, m), 4.00-4.25 (4H, m), 4.35-4.45 (1H, m), 6.10 (1H, d, J=7.1 Hz), 6.95 (1H, t, J=7.5 Hz), 7.09 (1H, t, J=7.5 Hz), 7.17 (1H, s), 7.28 (1H, d, J=7.8 Hz), 7.57 (1H, d, J=7.8 Hz), 8.00-8.20 (2H, m)

(3) Preparation of Compound 79

A solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(OH)-DNle-O^(t) Bu (11 mg, prepared in (1)) in methanol (3 ml) was treated with etherial diazomethane.

The mixture was evaporated in vacuo, and the residue was purified by silica gel chromatography (Wakogel, C-200) with hexane/ethyl acetate=3/2 for elution to give a pale yellow powder (8.2 mg). The product (7.9 mg) was dissolved in formic acid (0.4 ml) and the mixture was stirred at room temperature for 14 h. The reaction mixture was evaporated in vacuo and the residue was purified by preparative TLC (3M, Empore Silica Sheet) with chloroform/methanol=5/1 for development to give the product (4.1 mg).

m.p.: 115°-120° C.

High Resolution FAB-MS (m/e, (C₃₃ H₅₁ N₅ O₆ +H)⁺): Calcd: 614.3917 Found: 614.3881

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.79 (9H, s), 1.05 (6H, d, J=6.6 Hz), 0.80-1.80 (17H, m), 2.88 (1H, dd, J=9.1 Hz, 14.6 Hz), 3.13 (1H, dd, J=4.2 Hz, 14.6 Hz), 3.85-3.95 (1H, m), 4.10-4.25 (3H, m), 4.40-4.50 (1H, m), 3.98 (3H, s), 6.11 (1H, d, J=7.9 Hz), 7.01 (1H, t, J=7.5 Hz), 7.15 (1H, t, J=7.5 Hz), 7.29 (1H, s), 7.35 (1H, d, J=7.5 Hz), 7.59 (1H, d, J=7.5 Hz), 7.80-7.90 (1H, m), 7.90-8.05 (1H, m)

EXAMPLE 70 Synthesis of Compound 80, 81, 82 and 83 (1) Preparation of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OBzl)-DNle-O^(t) Bu

To a solution of 2,6-Dimethylpiperidinocarbonyl-γMeLeu-OH (64 mg), H-DTrp(7-OBzl)-OMe (61 mg) and HOBT.H₂ O (35 mg) in dichloromethane (2 ml) was added EDCI.HCl (44 mg) under ice cooling. The mixture was stirred at the same temperature for 3 h and at room temperature over night. The mixture was diluted with ethyl acetate (30 ml), washed with sat. aq. NaHCO₃, 1N-hydrochloric acid and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel chromatography (Merck, Kieselgel 60) with hexane/ethyl acetate=1/1 for elution to give 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OBzl)-OMe (75 mg). The compound (73 mg) was dissolved in methanol (2.0 ml) and 1N-aqueous sodium hydroxide solution (1.0 ml) was added under ice cooling. The mixture was stirred at the same temperature for 6 h and water (30 ml) was added. The mixture was acidified with 1N-hydrochloric acid and extracted with dichloromethane (30 ml×3). The combined organic layers were dried over MgSO₄ and evaporated to give 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OBzl)-OH (56 mg). To a mixture of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OBzl)-OH (55 mg), H-DNle-O^(t) Bu.HCl (26 mg) and HOBT.H₂ O (18 mg) in DMF (2 ml) were added NMM (13 μl) and EDCI.HCl (23 mg) under ice cooling. The mixture was stirred at the same temperature for 2 h and at room temperature for 3 h. Water (50 ml) was added to the mixture and the mixture was extracted with ethyl acetate (20 ml×3). The combined organic layers were washed with 10% aq. citric acid (20 ml), sat. aq. NaHCO₃ (20 ml) and brine (20 ml) successively, dried over MgSO₄ and evaporated in vacuo to give the product (72 mg).

FAB-MS (m/e, (C₄₈ H₆₃ N₅ O₆ +H)⁺): 746

(2) Preparation of Compound 80

To a solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OBzl)-DNle-O^(t) Bu (9.8 mg, prepared in (1)) in dichloromethane (0.5 ml) were added methyl chloroformate (10 μl), pulverized sodium hydroxide (5 mg) and TBAHS (2 mg), and the mixture was stirred at room temperature for 3 h. The mixture was diluted with dichloromethane, washed with water, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with hexane/ethyl acetate=1/1 for development to give 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(1-COOMe-7-OBzl)-DNle-O.sup.t Bu (5.4 mg). A solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(1-COOMe-7-OBzl)-DNle-O.sup.t Bu (5.1 mg, obtained above) in methanol (1 ml) was hydrogenated over 10% Pd/C (5 mg) at an atmospheric pressure of hydrogen for 1 h. After removal of the catalyst by filtration, the filtrate was evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with hexane/ethyl acetate=2/1 for elution. The product was dissolved in formic acid (1.0 ml) and the mixture was stirred at room temperature for 7 h. The reaction mixture was evaporated to give Compound 80 (1.1 mg).

High Resolution FAB-MS (m/e, (C₃₄ H₅₁ N₅ O₈ +H)⁺): Calcd: 658.3816 Found: 658.3829

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.85 (3H, t, J=7.0 Hz), 0.88 (9H, s), 1.14 (3H, d, J=7.0 Hz), 1.15 (3H, d, J=7.0 Hz), 1.07-2.13 (14H, m), 3.19 (1H, dd, J=5.3 Hz, 14.8 Hz), 3.31 (1H, dd, J=6.6 Hz, 14.8 Hz), 3.82-4.00 (2H, m), 4.05 (3H, s), 4.07-4.18 (1H, m), 4.23-4.33 (1H, m), 4.73-4.83 (1H, m), 4.87 (1H, d, J=6.2 Hz), 6.45 (1H, d, J=8.6 Hz), 6.89 (1H, d, J=7.3 Hz), 7.03 (1H, d, J=7.3 Hz), 7.18 (1H, t, J=7.3 Hz), 7.36 (1H, s), 7.78 (1H, d, J=7.4 Hz), 10.59 (1H, s)

(3) Preparation of Compound 81

A solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OBzl)-DNle-O^(t) Bu (60.6 mg, obtained in (1)) in methanol (5 ml) was hydrogenated over 10% Pd/C (20 mg) at an atmospheric pressure of hydrogen for 1 h. After removal of the catalyst by filtration, the filtrate was evaporated in vacuo to give 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OH)-DNle-O^(t) Bu (50.2 mg). A mixture of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OH)-DNle-O^(t) Bu (14.4 mg, obtained above) in formic acid (1.0 ml) was stirred at room temperature for 9 h. The mixture was evaporated and the residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol/acetic acid=30/1/1 for development to give Compound 81 (7.3 mg).

High Resolution FAB-MS (m/e, (C₃₂ H₄₉ N₅ O₆ +H)⁺): Calcd: 600.3761 Found: 600.3779

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.79 (3H, brs), 0.90 (9H, s), 1.00-1.84 (20H, m), 3.03-3.20 (1H, m), 3.27-3.46 (1H, m), 3.90-4.30 (4H, m), 4.70-4.90 (1H, m), 5.11 (1H, brs), 6.55-7.20 (7H, m), 9.44 (1H, brs)

(4) Preparation of Compound 82

A solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OH)-DNle-O^(t) Bu (33.9 mg, prepared in (3)) in diethyl ether (3 ml) and methanol (1 ml) was treated with etherial diazomethane. The reaction mixture was evaporated and the residue was purified by silica gel chromatography (Merck, Kieselgel 60) with hexane/ethyl acetate=1/1 for elution to give 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OMe)-DNle-O^(t) Bu (27.5 mg). A mixture of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OMe)-DNle-O^(t) Bu (4.8 mg) in formic acid (1.0 ml) was stirred at room temperature for 7 h. The mixture was evaporated and the residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol/acetic acid=30/1/1 for development to give Compound 82 (3.4 mg).

High Resolution FAB-MS (m/e, (C₃₃ H₅₁ N₅ O₆ +H)⁺): Calcd: 614.3918 Found: 614.3904

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.83 (3H, t, J=7.2 Hz), 0.88 (9H, s), 1.12 (6H, d, J=6.8 Hz), 1.00-1.92 (14H, m), 3.20 (1H, dd, J=5.7 Hz, 14.7 Hz), 3.45 (1H, dd, J=5.7 Hz, 14.7 Hz), 3.80-4.00 (2H, m), 3.94 (3H, s), 4.05-4.20 (1H, m), 4.20-4.32 (1H, m), 4.68-4.78 (1H, m), 4.99 (1H, brs), 6.56 (1H, brs), 6.63 (1H, d, J=7.8 Hz), 7.00 (1H, t, J=7.8 Hz), 7.07 (1H, s), 7.21 (1H, d, J=7.8 Hz), 7.55 (1H, brs), 8.54 (1H, brs)

(5) Preparation of Compound 83

To a solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OMe)-DNle-O^(t) Bu (17.9 mg, prepared in (3)) in dichloromethane (1.0 ml) were added methyl chloroformate (20 μl), pulverized sodium hydroxide (20 mg) and TBAHS (5 mg), and the mixture was stirred at room temperature for 3 h. The mixture was diluted with dichloromethane, washed with water, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with hexane/ethyl acetate=1/1 for development to give 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(1-COOMe-7-OMe)-DNle-O.sup.t Bu (12.4 mg). A mixture of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(7-OMe)-DNle-O^(t) Bu (9.2 mg) in TFA (1 ml) was stirred at room temperature for 1 h and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol/acetic acid=30/1/1 for development to give Compound 83 (8.1 mg).

High Resolution FAB-MS (m/e, (C₃₅ H₅₃ N₅ O₈ +H)⁺): Calcd: 672.3972 Found: 672.4007

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.84 (3H, t, J=7.0 Hz), 0.84 (9H, s), 1.15 (6H, d, J=6.8 Hz), 1.09-1.94 (14H, m), 3.25 (2H, d, J=6.4 Hz), 3.89-4.04 (2H, m), 3.95 (3H, s), 3.97 (3H, s), 4.11-4.22 (1H, m), 4.23-4.33 (1H, m), 4.66-4.77 (1H, m), 5.06 (1H, d, J=6.1 Hz), 6.66 (1H, d, J=6.5 Hz), 6.86 (1H, t, J=4.7 Hz), 7.19 (2H, d, J=4.7 Hz), 7.44 (1H, s), 7.63 (1H, d, J=7.8 Hz)

EXAMPLE 71 Synthesis of Compound 84

To a solution of Compound 40 (27 mg, prepared in Example 40) in methanol (0.5 ml) was added a solution of sodium bicarbonate (3.5 mg) in water (0.1 ml). The mixture was evaporated in vacuo and the residue was dissolved in DMF (0.5 ml). Iodomethane (0.2 ml) was added to the mixture, and the mixture was stirred at room temperature for 20 h. The mixture was evaporated in vacuo and the residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with hexane/ethyl acetate=1/1 for development to give the product (11 mg).

m.p.: 80°-88° C.

IR (KBr, cm⁻¹): 3412, 2956, 1746, 1656, 1623, 1560, 1521, 1461, 1386, 1341, 1260, 1092

High Resolution FAB-MS (m/e, (C₃₅ H₅₃ N₅ O₇ +H)⁺): Calcd: 656.4023 Found: 656.3996

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.82 (3H, t, J=7.2 Hz), 0.89 (9H, s), 1.05-1.85 (14H, m), 1.15 (3H, d, J=7.1 Hz), 1.16 (3H, d, J=6.8 Hz), 3.17 (1H, dd, J=5.7 Hz, 15.0 Hz), 3.39 (1H, dd, J=6.2 Hz, 15.0 Hz), 3.65 (3H, s), 3.90-4.06 (2H, m), 4.06-4.20 (1H, m), 4.36-4.47 (1H, m), 4.64 (1H, d, J=6.8 Hz), 4.78-4.90 (1H, m), 6.38 (1H, d, J=9.2 Hz), 7.27 (1H, brs), 7.25 (1H, t, J=7.3 Hz), 7.34 (1H, t, J=7.3 Hz), 7.47 (1H, s), 7.61 (1H, d, J=7.3 Hz), 8.17 (1H, d, J=7.3 Hz)

EXAMPLE 72 Synthesis of Compound 85

Compound 85 was prepared using iodoethane instead of iodomethane in the same manner described in Example 71.

m.p.: 80°-85° C.

IR (KBr, cm⁻¹): 3412, 2950, 1746, 1653, 1626, 1533, 1461, 1386, 1257, 1194, 1089, 465

High Resolution FAB-MS (m/e, (C₃₆ H₅₅ N₅ O₇ +H)⁺): Calcd: 670.4180 Found: 670.4161

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.82 (3H, t, J=7.2 Hz), 0.89 (9H, s), 1.05-1.85 (14H, m), 1.15 (3H, d, J=7.1 Hz), 1.16 (3H, d, J=7.1 Hz), 1.22 (3H, t, J=7.3 Hz), 3.17 (1H, dd, J=5.8 Hz, 14.7 Hz), 3.38 (1H, dd, J=6.1 Hz, 14.7 Hz), 3.90-4.05 (2H, m), 4.00 (3H, s), 4.09 (2H, dq, J=1.3 Hz, 7.2 Hz), 4.05-4.20 (1H, m), 4.35-4.45 (1H, m), 4.66 (1H, d, J=7.3 Hz), 4.75-4.88 (1H, m), 6.49 (1H, d, J=8.6 Hz), 7.18 (1H, d, J=7.3 Hz),), 7.24 (1H, t, J=7.3 Hz), 7.33 (1H, t, J=7.3 Hz), 7.48 (1H, s), 7.61 (1H, d, J=7.3 Hz), 8.17 (1H, d, J=8.0 Hz)

EXAMPLE 73 Synthesis of Compound 86

Compound 86 was prepared using 2-iodopropane instead of iodomethane in the same manner described in Example 71.

m.p.: 75°-80° C.

IR (KBr, cm⁻¹): 3400, 2950, 2872, 1745, 1656, 1623, 1527, 1461, 1386, 1341, 1311, 1260, 1197, 1146, 1107, 1092, 765

High Resolution FAB-MS (m/e, (C₃₇ H₅₇ N₅ O₇ +H)⁺): Calcd: 684.4337 Found: 684.4334

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.82 (3H, t, J=7.2 Hz), 0.88 (9H, s), 1.05-1.85 (14H, m), 1.15 (3H, d, J=6.8 Hz), 1.16 (3H, d, J=7.1 Hz), 1.19 (3H, d, J=6.3 Hz), 1.21 (3H, d, J=6.3 Hz), 3.17 (1H, dd, J=5.9 Hz, 14.9 Hz), 3.37 (1H, dd, 6.4 Hz, 14.9 Hz), 3.90-4.05 (2H, m), 4.00 (3H, s), 4.05-4.20 (1H, m), 4.31-4.42 (1H, m), 4.67 (1H, d, J=6.8 Hz), 4.75-4.86 (1H, m), 4.94 (1H, sept, J=6.3 Hz), 6.49 (1H, d, J=8.4 Hz), 7.12 (1H, d, J=7.6 Hz), 7.24 (1H, t, J=7.8 Hz), 7.33 (1H, t, J=7.8 Hz), 7.48 (1H, s), 7.62 (1H, d, J=7.8 Hz), 8.17 (1H, d, J=7.8 Hz)

EXAMPLE 74 Synthesis of Compounds 87 and 88

To a solution of Compound 84 (94 mg, prepared in Example 71) in dry THF (1 ml) were added lithium chloride (12.3 mg), sodium borohydride (11 mg) and dry ethanol (2 ml), and the mixture was stirred at room temperature over night. The mixture was cooled with ice-water, adjusted to pH 4 by the gradual addition of 10% aq. citric acid, and concentrated in vacuo. Water (20 ml) was added to the residue, and the mixture was extracted with dichloromethane (10 ml×3). Combined organic layers were washed with brine, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with ethyl acetate for development to give Compound 87 (21 mg) and Compound 88 (11 mg).

Compound 87

IR (KBr, cm⁻¹): 3400, 2950, 2866, 1743, 1653, 1620, 1536, 1461, 1386, 1260, 1092, 765

High Resolution FAB-MS (m/e, (C₃₄ H₅₃ N₅ O₆ +H)⁺): Calcd: 628.4074 Found: 628.4075

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.86 (3H, t, J=7.1 Hz), 0.87 (9H, s), 1.15 (3H, d, J=6.9 Hz), 1.16 (3H, d, J=6.9 Hz), 1.05-1.85 (14H, m), 3.22 (1H, dd, J=4.9 Hz, 14.8 Hz), 3.45 (1H, dd, J=6.1 Hz, 14.8 Hz), 3.45-3.65 (2H, m), 3.68-3.79 (1H, m), 3.79-3.98 (2H, m), 4.01 (3H, s), 4.04-4.17 (1H, m), 4.65 (1H, d, J=6.1 Hz), 4.75-4.86 (1H, m), 5.95 (1H, d, J=8.8 Hz), 7.16 (1H, d, J=8.1 Hz), 7.26 (1H, dt, J=1.3 Hz, 7.8 Hz), 7.36 (1H, dt, J=1.3 Hz, 7.8 Hz), 7.48 (1H, s), 7.59 (1H, dd, J=1.3 Hz, 7.8 Hz), 8.19 (1H, dd, J=1.3 Hz, 7.8 Hz)

Compound 88

IR (KBr, cm⁻¹): 3304, 2950, 2866, 1743, 1653, 1611, 1539, 1461, 1386, 1254, 1089, 1044, 756

High Resolution FAB-MS (m/e, (C₃₅ H₅₅ N₅ O₆ +H)⁺): Calcd: 642.4231 Found: 642.4227

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.85 (3H, t, J=7.0 Hz), 0.87 (9H, s), 1.15 (3H, d, J=7.1 Hz), 1.16 (3H, d, J=7.1 Hz), 1.05-1.83 (14H, m), 1.46 (3H, t, J=7.0 Hz), 3.23 (1H, dd, J=5.3 Hz, 14.8 Hz), 3.44 (1H, dd, J=6.2 Hz, 14.8 Hz), 3.45-3.65 (2H, m), 3.68-3.78 (1H, m), 3.78-3.98 (2H, m), 4.05-4.16 (1H, m), 4.40-4.53 (2H, m), 4.64 (1H, d, J=6.1 Hz), 4.73-4.85 (1H, m), 5.95 (1H, d, J=8.8 Hz), 7.15 (1H, d, J=8.1 Hz), 7.25 (1H, dt, J=1.2 Hz, 7.5 Hz), 7.35 (1H, dt, J=1.2 Hz, 7.5 Hz), 7.50 (1H, s), 7.59 (1H, dd, J=1.2 Hz, 7.5 Hz), 8.19 (1H, dd, J=1.2 Hz, 7.5 Hz)

EXAMPLE 75 Synthesis of Compounds 89 and 90

Compound 89 (ester form) and Compound 90 (deprotected form) were prepared using 2,6-dimethylpiperidine and H-Cpeg-OBzl.HCl instead of cyclopentylpropylamine and H-Leu-OBzl.TsOH in the same manner described in Example 36.

Compound 89

High Resolution FAB-MS (m/e, (C₃₈ H₅₇ N₅ O₇ +H)⁺): Calcd: 696.4337 Found: 696.4319

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.82 (3H, t, J=7.1 Hz), 0.96-1.81 (20H, m), 1.17 (6H, d, J=7.4 Hz), 1.41 (9H, s), 2.09-2.20 (1H, m), 3.21 (1H, dd, J=5.7 Hz, 14.7 Hz), 3.33 (1H, dd, J=6.5 Hz, 14.7 Hz), 3.64-3.75 (1H, m), 3.90-4.05 (1H, m), 4.12-4.24 (1H, m), 4.01 (3H, s), 4.25-4.35 (1H, m), 4.82 (1H, d, J=6.9 Hz), 4.80-4.93 (1H, m), 6.33 (1H, d, J=9.1 Hz), 7.16 (1H, d, J=7.8 Hz), 7.25 (1H, dt, J=1.4 Hz, 7.7 Hz), 7.33 (1H, dt, J=1.4 Hz, 7.7 Hz), 7.47 (1H, s), 7.63 (1H, dd, J=1.4 Hz, 7.7 Hz), 8.16 (1H, dd, J=1.4 Hz, 7.7 Hz)

Compound 90

High Resolution FAB-MS (m/e, (C₃₄ H₄₉ N₅ O₇ +H)⁺): Calcd: 640.3710 Found: 640.3607

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.86 (3H, t, J=6.9 Hz), 1.03 (3H, d, J=6.8 Hz), 1.05 (3H, d, J=6.8 Hz), 0.92-1.80 (20H, m), 1.80-1.91 (1H, m), 2.81 (1H, dd, J=11.6 Hz, 14.6 Hz), 3.30 (1H, dd, J=2.6 Hz, 14.6 Hz), 3.50-3.84 (2H, m), 3.96 (3H, s), 4.03-4.20 (2H, m), 4.50-4.62 (1H, m), 6.05 (1H, d, J=6.8 Hz), 7.25 (1H, dt, J=1.3 Hz, 7.3 Hz), 7.32 (1H, dt, J=1.3 Hz, 7.3 Hz), 7.53 (1H, s), 7.64 (1H, dd, J=1.3 Hz, 7.3 Hz), 8.05 (1H, dd, J=1.3 Hz, 7.3 Hz), 8.23 (1H, d, J=7.6 Hz), 8.33 (1H, d, J=8.8 Hz)

EXAMPLE 76 Synthesis of Compound 91

Compound 91 was prepared using H-DβAbu-O^(t) Bu instead of H-DNle-O^(t) Bu in the same manner described in Example 64.

m.p.: 122°-126° C.

High Resolution FAB-MS (m/e, (C₃₀ H₄₁ N₅ O₇ +H)⁺): Calcd: 584.3085 Found: 584.3079

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.03-0.42 (4H, m), 0.83-1.00 (1H, m), 1.07 (3H, d, J=6.8 Hz), 1.09 (3H, d, J=7.0 Hz), 1.13 (3H, d, J=6.6 Hz), 1.33-1.82 (6H, m), 2.15 (1H, dd, J=8.9 Hz, 15.0 Hz), 2.33-2.41 (1H, m), 2.75-2.90 (1H, m), 3.17-3.24 (4H, m), 3.96 (3H, s), 4.05-4.23 (1H, m), 4.34-4.46 (1H, m), 6.37 (1H, d, J=5.6 Hz), 7.26 (1H, t, J=7.1 Hz), 7.34 (1H, t, J=7.1 Hz), 7.50 (1H, s), 7.63 (1H, d, J=7.1 Hz), 7.92 (1H, d, J=7.1 Hz), 8.05 (1H, d, J=8.1 Hz), 8.60 (1H, d, J=8.6 Hz)

EXAMPLE 77 Synthesis of Compound 92 (1) Preparation of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(COOMe)-OH

To a solution of Boc-DTrp-OBzl (12.19 g) in dichloromethane (60 ml) were added methyl chloroformate (4.8 ml), pulverized sodium hydroxide (4.1 g) and TBAHS (9.2 g), and the mixture was stirred at room temperature for 4 h. The reaction mixture was washed with water, dried over MgSO₄ and evaporated in vacuo. The residue was crystallized from dichloromethane and hexane to give Boc-DTrp(COOMe)-OBzl (12.57 g). Boc-DTrp(COOMe)-OBzl (4.52 g) was dissolved in 4N-hydrogen chloride/1,4-dioxane (50 ml) and the mixture was stirred at room temperature for 45 min. Ethyl ether (50 ml) was added to the mixture to complete the precipitation. The precipitate was collected by filtration and dried in vacuo to give H-DTrp(COOMe)-OBzl.HCl (3.71 g). To a suspension of H-DTrp(COOMe)-OBzl.HCl (1.94 g) in dichloromethane (50 ml) were added NMM (0.55 ml), 2,6-dimethylpiperidinocarbonyl-γMeLeu-OH (1.42 g), HOBT.H₂ O (0.84 g) and EDCI.HCl (1.05 g) under ice cooling. The mixture was stirred at the same temperature for 2 h and at room temperature over night. The reaction mixture was washed with sat. aq NaHCO₃ (50 ml), 10% aq. citric acid (50 ml) and brine (50 ml) successively, dried over MgSO₄ and evaporated. The residue was purified by MPLC (Merck, LiChroprep Si 60) with hexane/ethyl acetate=2/1 for elution to give 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(COOMe)-OBzl (1.17 g). A solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(COOMe)-OBzl (1.10 g) in methanol (30 ml) was hydrogenated over 10% Pd/C (50 mg) at an atmospheric pressure of hydrogen for 1.5 h. After removal of the catalyst by filtration, the filtrate was evaporated in vacuo to give the product (0.93 g).

(2) Preparation of Compound 92

To a solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(COOMe)-OH (53 mg, prepared in (1)) and HOSu (17 mg) in DMF (1.0 ml) was added EDCI.HCl (29 mg) under ice cooling, and the mixture was stirred at the same temperature for 3.5 h. To the mixture was added a solution of glycine (11 mg) and NMM (16 μl) in water (1.0 ml). The mixture was stirred at the same temperature for 2 h and at room temperature over night. To the mixture was added 1N-hydrochloric acid (20 ml), and the mixture was extracted with dichloromethane (10 ml×3). The combined organic layers were washed with brine (10 ml), dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol/acetic acid=20/1/1 for development to give Compound 92 (23 mg).

m.p.: 124°-127° C.

IR (KBr, cm⁻¹): 2960, 1738, 1659, 1612, 1531, 1458, 1444, 1383, 1259, 1090, 766, 748

High Resolution FAB-MS (m/e, (C₃₀ H₄₃ N₅ O₇ +H)⁺): Calcd: 586.3241 Found: 586.3232

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.74 (9H, s), 1.16 (3H, d, J=6-8 Hz), 1.19 (3H, d, J=6.8 Hz), 1.31-1.82 (8H, m), 3.14 (1H, dd, J=10.0 Hz, 14.8 Hz), 3.49 (1H, dd, 4.4 Hz, 14.8 Hz), 3.74 (1H, dd, J=6.3 Hz, 16.7 Hz), 3.90-4.14 (3H, m), 3.97 (3H, s), 4.22 (1H, dd, J=6.3 Hz, 16.7 Hz), 4.77-4.93 (2H, m), 7.13-7.36 (3H, m), 7.51 (1H, s), 7.57 (1H, d, J=7.7 Hz), 7.87 (1H, t, J=6.3 Hz), 8.13 (1H, d, J=7.7 Hz)

Each Compound 93-95 in the following Examples 78-80 was prepared using each corresponding amino acid instead of glycine in the same manner described in Example 77.

EXAMPLE 78 Compound 93

m.p.: 113°-116° C.

IR (KBr, cm⁻¹): 3300, 2958, 1738, 1653, 1539, 1456, 1385, 1259, 1092, 766, 748

High Resolution FAB-MS (m/e, (C₃₁ H₄₅ N₅ O₇ +H)⁺): Calcd: 600.3397 Found: 600.3408

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.73 (9H, s), 1.17 (3H, d, J=6.9 Hz), 1.21 (3H, d, J=6.9 Hz), 1.10-2.10 (8H, m), 2.49-2.70 (2H, m), 3.14 (1H, dd, J=9.1 Hz, 14.7 Hz), 3.38 (1H, dd, 4.8 Hz, 14.7 Hz), 3.08-3.48 (2H, m), 3.73-3.89 (1H, m), 4.01 (3H, s), 3.94-4.18 (2H, m), 4.21-4.84 (2H, m), 7.13 (1H, d, J=9.3 Hz), 7.24 (1H, t, J=7.7 Hz), 7.31 (1H, t, J=7.7 Hz), 7.46 (1H, t, J=5.3 Hz), 7.52 (1H, s), 7.62 (1H, d, J=7.7 Hz), 8.13 (1H, d, J=7.7 Hz)

EXAMPLE 79 Compound 94

m.p.: 137°-141° C.

IR (KBr, cm⁻¹): 3400, 2956, 2576, 1734, 1653, 1522, 1456, 1385, 1259, 1092, 744

High Resolution FAB-MS (m/e, (C₃₉ H₅₀ N₆ O₇ +H)⁺): Calcd: 715.3819 Found: 715.3815

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.74 (9H, s), 1.03 (3H, d, J=6.7 Hz), 1.05 (3H, d, J=6.7 Hz), 1.00-1.78 (8H, m), 2.75-2.92 (1H, m), 3.07-3.32 (3H, m), 3.94 (3H, s), 4.02-4.26 (3H, m), 4.42-4.60 (2H, m), 6.05 (1H, d, J=7.9 Hz), 7.00 (1H, t, J=7.8 Hz), 7.06 (1H, t, J=7.8 Hz), 7.20 (1H, d, J=2.4 Hz), 7.23 (1H, t, J=7.8 Hz), 7.31 (1H, t, J=7.8 Hz), 7.33 (1H, d, J=7.8 Hz), 7.51 (1H, d, J=7.8 Hz), 7.49 (1H, s), 7.65 (1H, d, J=7.8 Hz), 8.04 (1H, d, J=7.8 Hz), 8.19 (1H, d, J=10.5 Hz), 8.37 (1H, d, J=7.6 Hz), 10.83 (1H, d, J=2.4 Hz)

EXAMPLE 80 Compound 95

m.p.: 103°-108° C.

IR (KBr, cm⁻¹): 3300, 2958, 2939, 1738, 1653, 1533, 1456, 1444, 1383, 1259, 1092, 766, 748

High Resolution FAB-MS (m/e, (C₃₅ H₅₃ N₅ O₇ +H)⁺): Calcd: 656.4023 Found: 656.4044

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.82 (3H, t, J=7.0 Hz), 0.83 (9H, s), 1.18 (3H, d, J=6.8 Hz), 1.19 (3H, d, J=6.8 Hz), 1.08-1.82 (14H, m), 2.40 (1H, dd, J=5.2 Hz, 15.4 Hz), 2.53 (1H, dd, J=6.7 Hz, 15.4 Hz), 3.22 (1H, dd, J=6.8 Hz, 14.9 Hz), 3.29 (1H, dd, J=6.8 Hz, 14.9 Hz), 3.86-4.24 (4H, m), 4.02 (3H, s), 4.67-4.79 (1H, m), 6.48 (1H, d, J=6.9 Hz), 7.16 (1H, brs), 7.21-7.40 (2H, m), 7.32 (1H, t, J=7.8 Hz), 7.48 (1H, s), 7.60 (1H, d, J=7.8 Hz), 8.16 (1H, d, J=7.8 Hz)

EXAMPLE 81 Synthesis of Compound 96

To a solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(COOMe)-OH (53 mg, prepared in Example 77-(1)) and HOSu (17 mg) in DMF (1.0 ml) was added EDCI.HCl (29 mg) under ice cooling, and the mixture was stirred at the same temperature for 3.5 h. To the mixture was added a solution of aminomethanesulfonic acid (17 mg) and NMM (16 μl) in water (1.0 ml). The mixture was stirred at the same temperature for 2 h and at room temperature over night. The mixture was purified by reverse phase MPLC (Merck, LiChroprep RP-18) with methanol/water(containing 0.1% TFA)=3/2 for elution to give the product (26 mg).

m.p.: 135°-140° C.

IR (KBr, cm⁻¹): 1782, 1737, 1666, 1547, 1458, 1385, 1259, 1207, 1169, 1092, 1041, 768

High Resolution FAB-MS (m/e, (C₂₉ H₄₃ N₅ O₈ S+H)⁺): Calcd: 622.2911 Found: 622.2953

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.73 (9H, s), 1.02 (3H, d, J=6.9 Hz), 1.03 (3H, d, J=6.9 Hz), 0.98-1.73 (8H, m), 2.88 (1H, dd, J=10.2 Hz, 15.1 Hz), 3.09 (1H, dd, 4.3 Hz, 15.1 Hz), 3.93 (3H, s), 3.82-4.40 (5H, m), 4.59-4.69 (1H, m), 5.93 (1H, brs), 7.22 (1H, t, J=7.7 Hz), 7.30 (1H, t, J=7.7 Hz), 7.52 (1H, s), 7.74 (1H, d, J=7.7 Hz), 8.03 (1H, d, J=7.7 Hz), 8.03 (1H, d, J=8.0 Hz), 8.44 (1H, t, J=6.1 Hz)

Each Compound 97-99 in the following Examples 82-84 was prepared using each corresponding aminosulfonic acid instead of aminomethanesulfonic acid in the same manner described in Example 81.

EXAMPLE 82 Compound 97

m.p.: 115°-120° C.

IR (KBr, cm⁻¹): 1780, 1738, 1666, 1549, 1456, 1385, 1259, 1209, 1168, 1041, 768, 748

High Resolution FAB-MS (m/e, (C₃₀ H₄₅ N₅ O₈ S+H)⁺): Calcd: 674.2626 Found: 674.2632

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.73 (9H, s), 1.03 (3H, d, J=6.2 Hz), 1.06 (3H, d, J=6.2 Hz), 1.18-1.80 (8H, m), 2.42-2.66 (2H, m), 2.88 (1H, dd, J=4.4 Hz, 10.6 Hz), 3.13-3.43 (3H, m), 3.94 (3H, s), 4.00-4.21 (2H, m), 4.30-4.80 (2H, m), 6.10 (1H, brs), 7.23 (1H, t, J=7.6 Hz), 7.32 (3H, t, J=7.6 Hz), 7.47 (1H, s), 7.84 (1H, d, J=7.6 Hz), 8.04 (1H, d, J=7.6 Hz), 8.08 (1H, t, J=5.5 Hz), 8.28 (1H, d, J=7.9 Hz)

EXAMPLE 83 Compound 98

m.p.: 141°-144° C.

IR (KBr, cm⁻¹): 3400, 2958, 1778, 1738, 1660, 1539, 1456, 1383, 1259, 1153, 1092, 1036, 768

High Resolution FAB-MS (m/e, (C₃₄ H₅₃ N₅ O₈ S+H)⁺): Calcd: 692.3693 Found: 692.3713

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.73 (9H, s), 0.83 (3H, t, J=6.7 Hz), 1.04 (3H, d, J=6.7 Hz), 1.05 (3H, d, J=6.7 Hz), 0.97-2.00 (14H, m), 2.42-2.53 (2H, m), 2.87 (1H, dd, J=10.6 Hz, 15.0 Hz), 3.21 (1H, dd, J=3.2 Hz, 15.0 Hz), 3.94 (3H, s), 3.90-4.37 (5H, m), 6.10 (1H, d, J=6.6 Hz), 7.24 (1H, t, J=7.4 Hz), 7.31 (1H, t, J=7.4 Hz), 7.51 (1H, s), 7.66 (1H, d, J=7.4 Hz), 7.75 (1H, d, J=8.5 Hz), 8.04 (1H, d, J=7.4 Hz), 8.21 (1H, d, J=7.7 Hz)

EXAMPLE 84 Compound 99

IR (KBr, cm⁻¹): 2954, 2866, 1778, 1738, 1666, 1539, 1477, 1456, 1383, 1257, 1169, 1092, 1041, 768, 748, 627

High Resolution FAB-MS (m/e, (C₃₃ H₅₁ N₅ O₈ S+H)⁺): Calcd: 678.3537 Found: 678.3507

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.72+0.75 (9H, s), 0.80-1.96 (23H, m), 2.80-2.93 (1H, m), 3.05-3.18 (1H, m), 3.93 (3H, s), 3.99-4.71 (5H, m), 5.88+6.01 (1H, brs), 7.21 (1H, t, J=8.0 Hz), 7.30 (1H, t, J=8.0 Hz), 7.72+7.75 (1H, d×2, J=8.0 Hz), 7.56 (1H, s), 7.83-8.12 (3H, m)

EXAMPLE 85 Synthesis of Compound 100

To a solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(COOMe)-OH (106 mg, prepared in Example 77-(1)), diethyl (R)-1-aminopentylphosphonate (67 mg) and HOBT.H₂ O (51 mg) in dichloromethane (10 ml) was added EDCI.HCl (73 mg) under ice cooling, and the mixture was stirred at room temperature for 16 h. The mixture was diluted with ethyl acetate, washed with 10% aq. citric acid, water, sat. aq. NaHCO₃ and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel chromatography (Merck, Kieselgel 60) with hexane/ethyl acetate=1/1 for elution to give the diethyl ester of Compound 100 (61 mg). To a solution of the diethyl ester (41 mg) in dichloromethane (0.8 ml) was added bromotrimethylsilane (0.8 ml) under ice cooling. The mixture was stirred at room temperature for 4 h, and concentrated in vacuo. The residue was dissolved in 90% acetone/water (5 ml). The mixture was stirred at 45 min and evaporated in vacuo. The residue was triturated with water to give Compound 100 (25 mg).

m.p.: 205°-210° C.

IR (KBr, cm⁻¹): 2954, 2949, 1736, 1649, 1524, 1458, 1383, 1259, 1092, 768

High Resolution FAB-MS (m/e, (C₃₃ H₅₂ N₅ O₈ P+H)⁺): Calcd: 678.3632 Found: 678.3674

¹ H-NMR (300 MHz, CD₃ OD, δ ppm): 0.82 (9H, s), 0.92 (3H, t, J=6.8 Hz), 1.13 (3H, d, J=6.8 Hz), 1.14 (3H, d, J=6.8 Hz), 1.20-2.00 (14H, m), 3.0-3.1 (1H, m), 3.3-3.4 (1H, m), 4.01 (3H, s), 4.05-4.30 (4H, m), 4.7-4.8 (1H, m), 7.25 (1H, t, J=7.3 Hz), 7.31 (1H, t, J=7.3 Hz), 7.53 (1H, s), 7.67 (1H, d, J=7.3 Hz), 8.12 (1H, d, J=7.3 Hz)

EXAMPLE 86 Synthesis of Compound 101

To a solution of Compound 40 (32 mg, prepared in Example 40), 2-aminoethanol (4 mg) and HOBT.H₂ O (10 mg) was added EDCI.HCl (13 mg) under ice cooling. The mixture was stirred at the same temperature for 1 h and at room temperature over night. The mixture was diluted with ethyl acetate (20 ml), washed with sat. aq. NaHCO₃ (20 ml), 10% aq. citric acid (20 ml) and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol=30/1 for development to give the product (23.5 mg).

m.p.: 106°-109° C.

IR (KBr, cm⁻¹): 1736, 1655, 1610, 1524, 1458, 1383, 1257, 1088, 1257, 1088, 766

High Resolution FAB-MS (m/e, (C₃₆ H₅₆ N₆ O₇ +H)⁺): Calcd: 685.4289 Found: 685.4280

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.78 (9H, s), 0.84 (3H, t, J=7.1 Hz), 1.13 (6H, d, J=7.1 Hz), 1.04-1.79 (13H, m), 2.00-2.15 (1H, m), 3.22-3.43 (4H, m), 3.55-3.80 (3H, m), 3.82-4.17 (2H, m), 4.04 (3H, s), 4.44-4.56 (2H, m), 4.59-4.71 (1H, m), 4.68 (1H, d, J=4.7 Hz), 6.31 (1H, d, J=6.8 Hz), 6.75 (1H, t, J=4.3 Hz), 7.28 (1H, t, J=7.8 Hz), 7.38 (1H, t, J=7.8 Hz), 7.52 (1H, s), 7.59 (1H, d, J=7.8 Hz), 7.73 (1H, d, J=9.0 Hz), 8.20 (1H, d, J=7.8 Hz)

EXAMPLE 87 Synthesis of Compound 102

Compound 102 was prepared by deprotection of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp-DNle-O^(t) Bu with formic acid.

m.p.: 149°-153° C.

IR (KBr, cm⁻¹): 3309, 2947, 1653, 1522, 1387, 743

High Resolution FAB-MS (m/e, (C₃₂ H₄₉ N₅ O₅ +H)⁺): Calcd: 584.3812 Found: 584.3788

¹ H-NMR (300 MHz, CD₃ OD, δ ppm): 0.8-1.9 (17H, m), 0.85 (9H, s), 1.13 (3H, d, J=7.1 Hz), 1.15 (3H, d, J=7.1 Hz), 3.2-3.4 (2H, m), 4.0-4.4 (4H, m), 4.7-4.8 (1H, m), 6.97 (1H, t, J=7.9 Hz), 7.05 (1H, t, J=7.9 Hz), 7.08 (1H, s), 7.29 (1H, d, J=7.9 Hz), 7.59 (1H, d, J=7.9 Hz)

EXAMPLE 88 Synthesis of Compound 103

Dry hydrogen chloride gas was bubbled into a solution of Compound 102 (70 mg) in formic acid (3 ml), and the mixture was stirred at room temperature for 2.5 h. The mixture was evaporated in vacuo and the residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol=10/1 for elution to give the product (45 mg).

m.p.: 132°-135° C.

IR (KBr, cm⁻¹): 2954, 1716, 1653, 1608, 1522, 1458, 1387, 795, 750

High Resolution FAB-MS (m/e, (C₃₃ H₄₉ N₅ O₆ +H)⁺): Calcd: 612.3761 Found: 612.3746

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.75 (9H, s), 0.78-0.89 (3H, m), 1.01 (3H, d, J=6.8 Hz), 1.02 (3H, d, J=6.8 Hz), 1.05-1.8 (14H, m), 2.85-3.00 (1H, m), 3.2-3.5 (2H, m), 3.95-4.20 (4H, m), 4.5-4.6 (1H, m), 6.03-6.09 (1H, m), 7.26-7.36 (2H, m), 7.51-7.62 (1H, m), 7.69 (1H, d, J=7.6 Hz), 7.95-8.25 (2.5H, m), 9.18 (0.5H, brs)

EXAMPLE 89 Synthesis of Compound 104

To a solution of Compound 81 (7.3 mg, prepared in Example 70) in dichloromethane (0.5 ml) were added acetyl chloride (1.3 μl) and DMAP (3.7 mg) under ice cooling. The mixture was stirred at the same temperature for 4 h and at room temperature for 2 h. Ethyl acetate (20 ml) was added to the mixture, and the mixture was washed with 1N-hydrochloric acid (20 ml) and brine (20 ml), dried over MgSO₄ and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol/acetic acid=20/1/1 for elution to give the product (2.2 mg).

High Resolution FAB-MS (m/e, (C₃₄ H₅₁ N₅ O₇ +H)⁺): Calcd: 642.3867 Found: 642.3851

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.83 (3H, t, J=7.0 Hz), 0.88 (9H, s), 1.14 (6H, d, J=5.8 Hz), 1.07-1.87 (13H, m), 2.12-2.42 (1H, m), 2.38 (3H, s), 3.18 (1H, dd, J=6.0 Hz, 14.4 Hz), 3.40 (1H, dd, J=6.0 Hz, 14.4 Hz), 3.93-4.30 (4H, m), 4.68-4.80 (1H, m), 4.95 (1H, d, J=6.0 Hz), 6.70 (1H, d, J=6.5 Hz), 6.96 (1H, d, J=7.6 Hz), 7.06 (1H, t, J=7.6 Hz), 7.06 (1H, s), 7.31 (1H, d, J=6.5 Hz), 7.49 (1H, d, J=7.6 Hz), 8.62 (1H, s)

EXAMPLE 90 Synthesis of Compound 105

To a solution of 2,6-dimethylpiperidinocarbonyl-γMeLeu-DTrp(COOMe)-OH (20 mg) and NMM (4.2 μl) in dry THF (2.0 ml) was added isopropyl chloroformate (5.3 μl) at -25° C. over 5 min. To the mixture was added a solution of (R)-5-(1-aminopentyl)-1H-tetrazole hydrochloride (10.9 mg) and NMM (6.3 μl) in dry THF (2.0 ml) at -20° C. The mixture was stirred at -20° C.--15° C. for 2 h and at 10° C. for 10 h, then concentrated under reduced pressure. The residue was partitioned between ethyl acetate (10 ml) and water (10 ml). The organic layer was washed with 1N-hydrochloric acid (10 ml×2) and water (10 ml), dried over anhydrous sodium sulfate and evaporated in vacuo. The residue was purified by preparative TLC (Merck, Kieselgel 60 F₂₅₄) with chloroform/methanol=20/1 for development to give the product (13.5 mg).

m.p.: 111°-116° C.

IR (KBr, cm⁻¹): 3400, 3300, 2942, 2870, 1659, 1612, 1529, 1456, 1383, 1259, 1091, 766, 748

High Resolution FAB-MS (m/e, (C₃₄ H₅₁ N₉ O₅ +H)⁺): Calcd: 666.4092 Found: 666.4113

¹ H-NMR (300 MHz, CDCl₃, δ ppm): 0.83 (9H, s), 0.88 (3H, d, J=6.7 Hz), 0.98 (3H, t, J=6.7 Hz), 0.99 (3H, d, J=6.7 Hz), 1.08-1.90 (13H, m), 2.16-2.30 (1H, m), 3.30-3.48 (2H, m), 3.54 (1H, quint, J=6.7 Hz), 3.61-3.82 (2H, m), 4.05 (3H, s), 4.62-4.73 (1H, m), 4.66 (1H, d, J=6.0 Hz), 5.44 (1H, dt, J=3.9 Hz, 9.7 Hz), 6.32 (1H, d, J=6.6 Hz), 7.30 (1H, t, J=7.4 Hz), 7.40 (1H, t, J=7.4 Hz), 7.54 (1H, s), 7.61 (1H, d, J=7.4 Hz), 7.94 (1H, d, J=9.7 Hz), 8.20 (1H, d, J=7.4 Hz)

Each Compound 106 and 107 in the following Examples 91 and 92 was prepared using 2,6-dimethylpiperidinocarbonyl-Val-DTrp(COOMe)-OH and each corresponding aminosulfonic acid as starting materials in the same manner described in Example 81.

EXAMPLE 91 Compound 106

IR (KBr, cm⁻¹): 3290, 2960, 2935, 1738, 1668, 1610, 1522, 1458, 1383, 1259, 1201, 1092, 768, 748

FAB-MS (m/e, (C₃₁ H₄₇ N₅ O₈ S+H)⁺): 650

¹ H-NMR (300 MHz, CD₃ OD, δ ppm): 0.52 (3H, d, J=6.8 Hz), 0.77 (3H, d, J=6.8 Hz), 0.80-1.00 (3H, m), 1.17+1.19 (3H×2,d×2, J=6.6 Hz), 1.10-1.85 (13H, m), 2.96 (1H, dd, J=11.2 Hz, 14.6 Hz), 3.30-4.50 (5H, m), 4.01 (3H, s), 4.75 (1H, dd, J=3.9 Hz, 11.2 Hz), 7.22-7.34 (2H, m), 7.54 (1H, s), 7.67 (1H, d, J=7.2 Hz), 8.10 (1H, d, J=8.1 Hz)

EXAMPLE 92 Compound 107

m.p.: 128°-131° C.

IR (KBr, cm⁻¹): 3273, 2960, 1778, 1736, 1662, 1541, 1456, 1382, 1259, 1201, 1039, 768, 748

High Resolution FAB-MS (m/e, (C₃₂ H₄₉ N₅ O₈ S+H)⁺): Calcd: 664.3380 Found: 664.3437

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.51 (3H, d, J=6.4 Hz), 0.65 (3H, d, J=6.4 Hz), 0.83 (3H, t, J=7.0 Hz), 1.07 (6H, d, J=6.5 Hz), 1.01-2.00 (13H, m), 2.40-2.55 (2H, m), 2.83 (1H, dd, J=11.0 Hz, 14.5 Hz), 2.23 (1H, dd, J=3.0 Hz, 14.5 Hz), 3.69-3.83 (1H, m), 3.95 (3H, s), 3.97-4.23 (3H, m), 4.35-4.48 (1H, m), 5.95 (1H, brs), 7.25 (1H, t, J=7.5 Hz), 7.32 (1H, t, J=7.5 Hz), 7.51 (1H, s), 7.66 (1H, d, J=7.5 Hz), 7.81 (1H, d, J=8.3 Hz), 8.03 (1H, d, J=7.5 Hz), 8.34 (1H, d, J=8.1 Hz)

Each Compound 108 and 109 in the following Examples 93 and 94 was prepared using 2,6-dimethylpiperidinocarbonyl-Leu-DTrp(COOMe)-OH and each corresponding aminosulfonic acid as starting materials in the same manner described in Example 81.

EXAMPLE 93 Compound 108

m.p.: 139°-142° C.

IR (KBr, cm⁻¹): 3271, 2956, 2871, 1774, 1736, 1655, 1543, 1458, 1383, 1259, 1092, 1039, 768

High Resolution FAB-MS (m/e, (C₃₃ H₅₁ N₅ O₈ S+H)⁺): Calcd: 678.3537 Found: 678.3585

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.67 (3H, d, J=5.6 Hz), 0.71 (3H, d, J=5.6 Hz), 0.83 (3H, t, J=6.8 Hz), 1.04 (3H, d, J=6.7 Hz), 1.05 (3H, d, J=6.7 Hz), 1.10-2.00 (15H, m), 2.45-2.65 (2H, m), 2.85 (1H, dd, J=10.8 Hz, 14.5 Hz), 3.22 (1H, dd, J=3.4 Hz, 14.5 Hz), 3.95 (3H, s), 3.95-4.45 (5H, m), 6.07 (1H, brs), 7.24 (1H, t, J=7.6 Hz), 7.32 (1H, t, J=7.6 Hz), 7.47 (1H, s), 7.66 (1H, d, J=7.6 Hz), 7.78 (1H, d, J=8.5 Hz), 8.04 (1H, d, J=7.6 Hz), 8.21 (1H, d, J=7.8 Hz)

EXAMPLE 94 Compound 109

IR (KBr, cm⁻¹): 3271, 2956, 2872, 1738, 1668, 1610, 1539, 1456, 1385, 1259, 1203, 1092, 1041, 768

High Resolution FAB-MS (m/e, (C₃₂ H₄₉ N₅ O₈ S+Na)⁺): Calcd: 686.3187 Found: 686.3200

¹ H-NMR (300 MHz, DMSO-d₆, δ ppm): 0.57-0.89 (9H, m), 0.95-1.10 (6H, m), 1.10-1.97 (15H, m), 2.78-2.93 (1H, m), 3.09-3.31 (1H, m), 3.94+3.95 (3H, s×2), 4.00-4.75 (8H, m), 5.85+6.10 (1H, brs×2), 7.18+7.54 (1H, brs×2), 7.20-7.36 (2H, m), 7.46+7.55 (1H, s×2), 7.64+7.76 (1H, d×2, J=7.3 Hz), 8.03+8.05 (1H, d×2, J=7.3 Hz), 7.95+8.33 (1H, d×2, J=9.8 Hz, 8.8 Hz)

REFERENTIAL EXAMPLE 1 Synthesis of (R)-2-Aminohexanesulfonic acid (1) Preparation of (R)-2-t-butoxycarbonylamino-1-hexanol

To a solution of Boc-DNle-OMe (4.23 g) in dry THF (30 ml) were added lithium chloride (0.85 g), sodium borohydride (0.76 g) and dry ethanol (60 ml), and the mixture was stirred at the same temperature for 2 h and at room temperature over night. The mixture was cooled with ice-water, adjusted to pH 3 by the gradual addition of 10% aq. citric acid, and concentrated in vacuo. Water (200 ml) was added to the residue, and the mixture was extracted with dichloromethane (50 ml×3). The combined organic layers were washed with brine, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel chromatography (Merck, Kieselgel 60) with hexane/ethyl acetate=1/1 for elution to give the product (2.95 mg).

(2) Preparation of (R)-2-t-butoxycarbonylamino-1-hexyl methanesulfonate

To a solution of (R)-2-t-butoxycarbonylamino-1-hexanol (2.17 g, prepared in (1)) in dichloromethane (20 ml) were added triethylamine (1.67 ml) and methanesulfonyl chloride (0.93 ml) under ice cooling. After being stirred at the same temperature for 1 h, the mixture was washed with water, 10% aq. citric acid, sat. aq NaHCO₃ and brine successively, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel chromatography (Merck, Kieselgel 60) with hexane/ethyl acetate=2/1 for elution to give the product (1.32 g).

(3) Preparation of (R)-2-aminohexanesulfonic acid

A mixture of (R)-2-t-butoxycarbonylamino-1-hexyl methanesulfonate (428 mg, prepared in (1)) in 4N-hydrogen chloride/1,4-dioxane (10 ml) was stirred at room temperature for 1 h, and evaporated in vacuo. The residue was dissolved in water (3.0 ml) and sodium sulfite (378 mg) was added. After being stirred at room temperature for 4 d, the reaction mixture was passed through a Dowex 50W-X8 column (H⁺ form) and washed with excess water. The combined water solution was concentrated in vacuo to give the product (114 mg).

FAB-MS (m/e, (C₆ H₁₅ NO₃ S+H)⁺): 182

REFERENTIAL EXAMPLE 2 Synthesis of (R)-3-Aminoheptanoic acid (1) Preparation of (R)-2-t-butoxycarbonylaminoheptanenitrile

A mixture of (R)-2-t-butoxycarbonylamino-1-hexyl methanesulfonate (561 mg, prepared in Referential Example 1-(2)) and sodium cyanide (117 mg) in DMF (3 ml) was stirred at 60° C. for 5 h. After cooling, water (50 ml) was added to the mixture. The mixture was extracted with dichloromethane (25 ml×3). Combined organic layers were washed with brine, dried over MgSO₄ and evaporated in vacuo. The residue was purified by silica gel chromatography (Merck, Kieselgel 60) with hexane/ethyl acetate=3/1 for elution to give the product (327 mg).

(2) Preparation of (R)-3-aminoheptanoic acid

A mixture of (R)-2-t-butoxycarbonylaminoheptanenitrile (165 mg, prepared in (1)) in 6N-hydrochloric acid (10 ml) was refluxed for 3 h. After cooling, the mixture was evaporated in vacuo. The residue was dissolved in methanol (2 ml) and propylene oxide (1 ml) was added to the mixture. After being stirred at room temperature over night, the mixture was evaporated in vacuo. The residue was crystallized from methanol and diethyl ether to give the product (52 mg).

FAB-MS (m/e, (C₇ H₁₅ NO₂ +H)⁺): 146 

What is claimed is:
 1. A peptide of the formula: ##STR125## wherein A is a group of the formula R¹² R¹³ N--C(═O)--, whereinR¹² is a lower alkyl group, a cycloalkyl group, a 1-adamantyl group, a phenyl group, a phenyl group wherein one or two hydrogen atoms on the phenyl ring is independently replaced by a halogen atom, a trifluoromethyl group, a nitro group, an amino group or a formylamino group, a pyridyl group, or a thienyl group, R¹³ is a hydrogen atom, a lower alkyl group or a cycloalkyl group, or R¹² and R¹³ form, together with the adjacent nitrogen atom, a 5- to 9-membered nitrogen-containing saturated heterocyclic ring having 4 to 8 carbon atoms, said heterocyclic ring wherein among methylene groups forming the ring, one methylene group not adjacent to the above nitrogen atom is replaced by a thio group, said heterocyclic ring wherein one to four hydrogen atoms on the carbon atoms of the heterocyclic ring is independently replaced by a lower alkyl group, or said heterocyclic ring wherein two adjacent carbon atoms in the heterocyclic ring form a benzo-fused ring; B is an oxygen atom or a group of the formula --NR² --, wherein R² is a hydrogen atom or a lower alkyl group; R³ is a lower alkyl group, a cycloalkyl group, an aryl group, a heterocyclic group, a cycloalkyl lower alkyl group, an aryl lower alkyl group or a heterocyclic lower alkyl group; X¹ is an oxygen atom or a group of the formula --NR⁴ --, wherein R⁴ is a hydrogen atom or a lower alkyl group; R⁵ is a (a) 3-indolylmethyl, (b) 3-benzothienylmethyl, (c) 1-naphthylmethyl, (d) benzyl group or (e) said (a), (b), (c) or (d) groups wherein one or two hydrogen atoms on the aromatic ring of the group is replaced by a hydroxyl group, a formyl group, a lower alkyl group, a lower alkoxy group, a lower alkoxycarbonyl group, a nitro group or a group of the formula R⁵¹ --CO--X², wherein R⁵¹ is a lower alkyl group, a lower alkoxy group, an amino group or an amino group which is substituted by a lower alkyl group, and X² is an oxygen atom or a group of the formula --NR⁵² --, wherein R⁵² is a hydrogen atom or a lower alkyl group; X³ is an oxygen atom or a sulfur atom; R⁶ is a hydrogen atom, a lower alkyl or lower alkenyl group, or lower alkyl or lower alkenyl group which has a substituent selected from the group consisting of a hydroxyl group, a lower alkoxy group, a lower alkylthio group and a heterocyclic group; n is 0 or 1; Y is (a) a hydroxymethyl group, (b) a group of the formula CO₂ R⁷¹ wherein R⁷¹ is a hydrogen atom or a lower alkyl group, (c) a group of the formula CONHR⁷² wherein R⁷² is a hydrogen atom, a lower alkyl group or lower alkyl group which has have a substituent selected from the group consisting of a hydroxyl group, a carboxyl group and a sulfo group, (d) a 1H-tetrazol-5-yl group, (e) a sulfo group and (f) a phosphono group; or a pharmaceutically acceptable salt thereof.
 2. The peptide of claim 1, whereinR⁵ is a 3-indolylmethyl group, wherein the indole ring is substituted at the 1-position and/or 2-position by one or two substituents selected from the group consisting of a lower alkoxy group, a lower alkanoyloxy group and a lower alkoxy carbonyl group; and R⁶ is a lower alkyl group, a lower alkenyl group or a lower alkyl or lower alkenyl group which has a substituent selected from the group consisting of a lower alkoxy group and a lower alkylthio group.
 3. The peptide of claim 1, wherein R⁵ is a substituted or unsubstituted 3-indolylmethyl group.
 4. The peptide of claim 1, wherein R⁵ is a substituted or unsubstituted 3-benzothienylmethyl group.
 5. The peptide of claim 1, wherein R⁵ is a substituted or unsubstituted 1-naphthylmethyl group.
 6. The peptide of claim 1, wherein R⁵ is a substituted or unsubstituted benzyl group.
 7. The peptide of claim 1, wherein Y is a hydroxymethyl group.
 8. The peptide of claim 1, wherein Y is a group of the formula CO₂ R⁷¹.
 9. The peptide of claim 1, wherein Y is a group of the formula CONHR⁷².
 10. The peptide of claim 1, wherein Y is a 1H-tetrazol-5-yl group.
 11. The peptide of claim 1, wherein Y is a sulfo group.
 12. The peptide of claim 1, wherein Y is a phosphono group.
 13. The peptide of claim 1, wherein A is R¹² R¹³ N--C(═O)--, wherein R¹² is a lower alkyl group and R¹³ is selected from the group consisting of a lower alkyl group and a cycloalkyl group, or R¹² and R¹³ form, together with the adjacent nitrogen atom, a 5- to 9-membered nitrogen-containing saturated heterocyclic ring having 4 to 8 carbon atoms, or said heterocyclic ring wherein one to four hydrogen atoms of the heterocyclic ring is independently replaced by a lower alkyl group.
 14. The peptide of claim 1, wherein A is R¹² R¹³ N--C(═O)--, wherein R¹² is a phenyl group, or said phenyl group wherein 1 or 2 hydrogen atoms on the phenyl ring is, independently, replaced by a halogen atom, a trifluoromethyl group, a nitro group, an amino group or a formylamino group and R¹³ is a hydrogen atom.
 15. The peptide of claim 13, wherein R⁵ is a group of the formula ##STR126## wherein R is lower alkyl.
 16. The peptide of claim 14, wherein R⁵ is a group of the formula ##STR127## wherein R is a lower alkyl group.
 17. A peptide of the formula: ##STR128## wherein A is a group of the formula R¹¹ O--CO--, wherein R¹¹ is a lower alkyl group or a phenyl group;B is an oxygen atom or a group of the formula --NR² --, wherein R² is a hydrogen atom or a lower alkyl group; R³ is a lower alkyl group, a cycloalkyl group, an aryl group, a heterocyclic group, a cycloalkyl lower alkyl group, an aryl lower alkyl group or a heterocyclic lower alkyl group; X¹ is an oxygen atom or a group of the formula --NR⁴ --, wherein R⁴ is a hydrogen atom or a lower alkyl group; R⁵ is a (a) 3-indolylmethyl, (b) 3-benzothienylmethyl, (c) 1-naphthylmethyl, (d) benzyl group or (e) said (a), (b), (c) or (d) group wherein one or two hydrogen atoms on the aromatic ring of the group is replaced by a hydroxyl group, a formyl group, a lower alkyl group, a lower alkoxy group, a lower alkoxycarbonyl group, a nitro group or a group of the formula R⁵¹ --CO--X², wherein R⁵¹ is a lower alkyl group, a lower alkoxy group, an amino group or an amino group which is substituted by a lower alkyl group, and X² is an oxygen atom or a group of the formula --NR⁵² --, wherein R⁵² is a hydrogen atom or a lower alkyl group; X³ is an oxygen atom or a sulfur atom; R⁶ is a hydrogen atom, a lower alkyl or lower alkenyl group, or a lower alkyl or alkenyl group which has a substituent selected from the group consisting of a hydroxyl group, a lower alkoxy group, a lower alkylthio group and a heterocyclic group; n is 0 or 1; Y is (a) a hydroxymethyl group, (b) a group of the formula CO₂ R⁷¹ wherein R⁷¹ is a hydrogen atom or a lower alkyl group, (c) a group of the formula CONHR⁷² wherein R⁷² is a hydrogen atom, a lower alkyl group or a lower alkyl group which has a substituent selected from the group consisting of a hydroxyl group, a carboxyl group and a sulfo group, (d) a 1H-tetrazol-5-yl group, (e) a sulfo group and (f) a phosphono group; or a pharmaceutically acceptable salt thereof.
 18. The peptide of claim 17, whereinR⁵ is a 3-indolylmethyl group, wherein the indole ring is substituted at the 1-position and/or 2-position by one or two substituents selected from the group consisting of a lower alkoxy group, a lower alkanoyloxy group and a lower alkoxy carbonyl group; and R⁶ is a lower alkyl group, a lower alkenyl group or a lower alkyl or lower alkenyl group which has a substituent selected from the group consisting of a lower alkoxy group and a lower alkylthio group.
 19. The peptide of claim 17, wherein R⁵ has the formula ##STR129## wherein R is a lower alkyl group.
 20. A bronchodilator pharmaceutical composition, comprising the peptide of claim 1 or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier.
 21. A bronchodilator pharmaceutical composition, comprising the peptide of claim 17 or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier.
 22. A method of inhibiting the binding of endothelin to its ET_(B) receptor in a mammal producing or secreting excess endothelin, comprising administering to a mammal in need thereof, a pharmaceutically effective amount of the peptide of claim 1 or a pharmaceutically acceptable salt thereof.
 23. A method of inhibiting the binding of endothelin to its ET_(B) receptor in a mammal producing or secreting excess endothelin, comprising administering to a mammal in need thereof, a pharmaceutically effective amount of the peptide of claim 13 or a pharmaceutically acceptable salt thereof.
 24. A method of inhibiting the binding of endothelin to its ET_(B) receptor in a mammal producing or secreting excess endothelin, comprising administering to a mammal in need thereof, a pharmaceutically effective amount of the peptide of claim 14 or a pharmaceutically acceptable salt thereof.
 25. A method of inhibiting the binding of endothelin to its ET_(B) receptor in a mammal producing or secreting excess endothelin, comprising administering to a mammal in need thereof, a pharmaceutically effective amount of the peptide of claim 15 or a pharmaceutically acceptable salt thereof.
 26. A method of inhibiting the binding of endothelin to its ET_(B) receptor in a mammal producing or secreting excess endothelin, comprising administering to a mammal in need thereof, a pharmaceutically effective amount of the peptide of claim 16 or a pharmaceutically acceptable salt thereof.
 27. A method of inhibiting the binding of endothelin to its ET_(B) receptor in a mammal producing or secreting excess endothelin, comprising administering to a mammal in need thereof, a pharmaceutically effective amount of the peptide of claim 17 or a pharmaceutically acceptable salt thereof. 